The solar oven principle worked really well in the back of my Firebird. That was ideal in the desert.
Great! I found the best place to buy dwarf citrus trees and it’s in south Texas and they use Texas A&M standards.
Their website is down for maintenance but you can still look at all their options. If you want the tree to be smaller, put it in a smaller container - this is all explained and how to care for the dwarf trees is there, too. For Texas and southern states, I believe this is the place to go, however they do ship to northern states. They ship fruiting age trees, no long wait for fruit.
Take a look at what they have at:
http://www.citrustreesonline.com/