30#.....heavy weight roofing felt. Big box stores carry it...but if you're out in Salisbury go to Herrington inc out in Hillsdale, NY....not the Millerton store. They have a good stone and masonry yard in Hillsdale, and there is everything you need for oven building....flues, fireclay or Heatstop 50, firebrick. Not sure about perlite or vermiculite, but Agway might. Or ask the guys in the masonry office, they are very helpful.
I lived in Goshen, CT...my friend and next door neighbor is a promenent memeber of the MHA, and well known masonry heater builder and an excellent soapstone fabricator. If you wanted any soapstone he sells slabs. I'll be up there sometime this late spring or summer...can't wait visit New England again.