I had thought about using a used commercial warming oven (like they use in restaurants to keep cooked food up to temp). Some of them are pretty tall, 5 to 6 feet even, and will reach up to 350*. And most of them I've seen are electric. Only thing is, I don't know if that's hot enough to cure powder coat or if the thermostats can be rewired (or replaced) to do so. I found a few on the 'bay pretty reasonably priced, 'tho.