The equipment you are referring to is only available from Europe; however, sometimes you can find them on e-Bay. They were generally used as a potato kiosk. Convection ovens work just fine for baking potatoes evenly. They are more expensive that conventional ovens but can easily handle volume, cook uniformly and result in a crispy outer skin. If you have a lot more money, you can buy some of the Rational ovens which speed up the cooking quite a bit.

Just look in the yellow pages for foodservice distributors. Some that come to mind are Costa and Sysco, but there are many servicing the area as well as a strong terminal market in Boston.