I think you're going to have to buy something for this one man.
At my workplace, we use a lot of resistance heater "hot plates", called black bodies.
Anyways, i've seen two different controllers around to control the temp. One is made by this company called Arroyo, which looks REALLY nice and REALLY expensive. The other one is some rig that somebody made themselves, and judging from the amount of work it looks like they put into it, I don't think you're going to want to mess with trying to make one yourself.
Of course, the ones at work have nice little LCD outputs, rotary encoders, and RS232 ports for control, so maybe if you obviate those parts of the setup, making one might be more manageable.