Alex, I can't help you with the Chinese, but I can point you towards an appropriate stone for the deck.
The best (and usually cheapest) stones for deck pizza ovens are cordierite kiln shelves. Any ceramic equipment supplier should carry them.
Before you buy stones, though, I think it's very important to take a long hard look at the oven and make sure it can both reach the temps it will need to reach (for NY style, at least 650 F) and that it puts out enough heat to recover well between pizzas. If electric, you want to look at wattage, and, if gas, BTUs. It's also to essential to look at broiling elements/burners, broiling element burner strength, as well as making sure the oven has separate controls for broiling and baking.
Lastly, if you're selling slices, you want to make sure you're getting an oven that's large enough to handle an appropriately sized slice pie. Slice pies really need to be a minimum of 18", with, imo 21" being ideal.
Btw, I recall reading somewhere that you were running a small operation. Some of the favorite commercial ovens in this forum are countertop ovens made in China. The only downside is that they only fit one pizza at a time, but I think it might be enough for your needs. Rather than shipping the oven from China to California and then to a U.S. destination, perhaps the seller might ship it directly to you and give you a break on pricing. Maybe.
Here's the oven I'm talking about:http://www.ebay.com/itm/COUNTERTOP-PIZZA-OVEN-PD14-A-400-/120807414517