Baker's Pride is a popular brand of pizza oven
This one here looks like it's suited to your tasks:http://cgi.ebay.com/452-BAKERS-PRIDE...ayphotohosting
At 1 1/2" thick, the baking stone is a little thin for my tastes, but it's not the end of the world. As I mentioned before, the thicker the stone, the less impact opening/closing the oven door will have on the oven temp. A thicker stone will also, imo, make a puffier crust/superior crust. Thicker stones will take longer to preheat, though. They'll also be more expensive to replace and weigh a ton be harder to transport. No matter what you do, don't go thinner than 1 1/2. Thinner than 1 1/2 and you'll be talking seriously impaired pizzas, imo.
You definitely want a gas oven.
Most Vulcan style pizzeria ovens are run in the 550 range, but my recommendation would be to go higher than that. At least from a perspective of the best pizza. The higher the temp, the better the oven spring, the puffier the crust. The extreme of this is the amazingly puffy crust of the 800+ deg. hearth wood oven Neopolitan pie.