Heres what I would do. Go to wall mart, buy about 3- 4 or more 20 dollar toaster ovens. Take out the heating coils, there may be 2 per oven, both same size and everything, get everything from them just leaving the cases. Build a good sized box out of metal, somthing about 14 gauge would be ok. Pop rivit it togther. cut out a door and hinge it and put a slide bolt lock on it. Take your toaster oven guts and place only the coils inside, drill holes for the wiring to come out, build a small switch box on it to mount the on off switch/ temp control switches if your ovens have them, some do, some don't. Use a standard 110 light switch for the switch, wire all of the hot wires to it, then to a heavy duty lead cord with 6.5' cut off it ( 3' is standard, 6.5' will give you what you need ) ( I think hot is black but, the back of the switch tells, wire the others togther then wire that into the heavy duty lead cord. Don't do anything with the ground, cut it off, If you wire it to the switch, you will ground everything out, and it will trip the breaker every time ( remember the box is metal ). Just space the coils evenly througout the box and you could get it to the needed temp, isn't it 400*?. Ya could put in a probe style temp gauge on it, if ya welded in a 1/4" bung. Just a thought