The so-called "white" oven, where the combustion happens in a firebox outside the baking chamber, is commercially produced, mostly in conjunction with a home heating scheme. This is one example:
http://mha-net.org/msb/html/bakeov03.htm
If you must have a "white" oven, you might want to consider one of the thousands of cast iron wood kitchen stoves that were produced in this country in the 19th century. A lot of those fireboxes are in bad shape, but could be rebuilt with some firebrick and home welding. But at the end of the day, how much do these things differ from putting some bricks in the bottom of your kitchen gas oven?
A lot of folks here would advocate using a traditional "fire in the hole" traditional bake oven. They come in really small sizes. here's an 18 incher made by superior clay:
http://www.superiorclay.com/oven/ovenkits.html
Again, the common wisdom about ovens that small is that they are not worth the trouble. The reason: To have room for a fire, and a pizza, and room to turn it around, 3 feet is about the minimum.
David