Berries can be found in a number of places, but you may have to special order and order in bulk. The places with the best selection are organic food stores, or specialty healthy food stores, though you may have to ask how to order 25 or 50 pound bags. The organic food store near me lets you preorder in bulk online, and you pick it up a few days later. If you just want to get started, Whole Foods sells them in the bulk food section where you use their scoop to put it in a bag - the price near me is surprisingly good, but not really suited to getting more than a few pounds at a time in their bags. They may let you buy in bulk, but since most of their stuff is quite expensive, I don't shop there much. Another option is the church of the Latter Day Saints LDS- they have food stores located in many parts of the country, though none near me, and you don't have to be a member to shop there.
As to mills, my favorite is the Lee Household Mill - you would want the S-600 or S-500 - both let you adjust the coarseness, the S - 600 is more powerful. They come up pretty regularly on ebay,( this one is pretty complete, though it is missing the lid for the hopper
http://www.ebay.com/itm/LEE-HOUSEHOLD-FLOUR-MILL-MODEL-S600-w-bag-/142277088369?hash=item2120601471:g:wxUAAOSwfVpYoP5j ) the white colored models are newer vintage, the grey ones are older, but so far every one except one has worked fine. One had a motor that would run for a few minutes then overheat and shut down, unfortunately it is not cost effective to rewind the motor, and the arbor is pretty specific so a motor replacement is pretty expensive. Like anything on ebay, it really pays off to search a number of completed listings before bidding, so you get a good idea of a fair price, and what should be included. Most commonly they are offered without a collection bag - which is pretty easy to replace by getting a vacuum bag from Home Depot, and often without a hopper, a little harder to replace, but I make them out of old juice jugs and an adapter. The benefit of the Lee is that it mills flour unbelievably fine, and is the best engineered, IMO - it uses air to basically hurl the berries at a stone over and over until the flour passes through a mesh at the rear of the machine. Most other mills that use a stone have one stone turning above, or next to, a fixed stone, and there is an adjustment that changes the distance between the two stones. Since the two stones are never exactly coplanar, IMO, you get more variety in the size of the flour being discharged in comparison to the Lee. The downside of the Lee is that it uses a universal motor, which can wear out. Most stone mills use a heavy duty universal motor, which last a very long time.
For stone mills, the two main options are horizontal stones or vertical. The All Grain Mill is probably the most compact - this is the older style
http://www.ebay.com/itm/ALL-GRAIN-Electric-Flour-Mill-MODEL-A33-Home-Brewing-or-Baking-Good-Condition-/252844530535?hash=item3adeb55b67:g:ALoAAOSwTM5Y49L3 the hopper is built into the machine, but you would have to add a flour bag, and the adjustment of the distance between the stones is not very precise. This is the newer style,
http://www.ebay.com/itm/Vintage-Commercial-ALL-GRAIN-FlourMill-Wheat-Grinder-A-22-Brigham-Ut-Free-Ship-/112398556463?hash=item1a2b79dd2f:g:ueAAAOSwdjNZBMJq the discharge chute has gone from round to a rectangle that is designed to fit on a plastic bin - which you can still order I think, though they are about $50. You can fabricate a collection bin, but it is pretty hard. The advantage is that the distance between the stones is set with a lever on the bottom and is much more precise.
There are a number of other machines where the stones are front and back, not top and bottom - this one shows a great photo of the two stones
http://www.ebay.com/itm/MARATHON-UNI-MILL-GRAIN-GRINDER-FLOUR-MAKER-LOOKS-UNUSED-POWERFUL-USA-MADE-MOTOR-/252920324880?hash=item3ae339e310:g:w5kAAOSwcOFWboEb There were tons of makers of these, and all the same principle, heavy duty induction motor, and two stones, with a hopper on top and a flour bin on bottom and an adjustment wheel, usually on the front. Some don't like them since the flour drops into a bin, not a bag, so there is some residual flour always in the machine and some escapes into the air, though I don't see it as a big problem. The major issue is that the machine is pretty heavy, and has a big footprint. Unlike the ones with external hoppers or bags, usually these machines usually are complete.
Many people believe impact machines heat up the grain too much, not sure if that is true, but they are extremely loud, even when they are not grinding flour, and use universal motors that make buying used a little more risky.
If you have a KA, they make an attachment called the Mock Mill - I have never used it, but read a few positive reviews, it uses smaller stones than a typical machine, so the output would be slower, but it is under $200 new
https://smile.amazon.com/dp/B00ZRLIHRK/?tag=pmak-20Any other questions, let me know. There are not many people into home milling, but the more I can drive that up, the better . BTW, once you get a mill, pretty soon you will stop buying bread at the store, since home milled bread tastes so much better.
