My partner (who's main job is designing experiments in an advanced physics lab) has picked up many Omega PID temp. controllers for cheap off of ebay over the years. They have worked great for all uses he and I have ever had for them, including a high temp. kiln.
The other day, I stopped by the shop I used to work at just to say hi, and I ended up getting roped into setting up their heat treat oven with a digital temp. controller because my little experience with them was more than their none. My old boss wanted it done immediately, and as cheaply as possible.
He wanted to order whatever was needed from McMaster because he needed other stuff from there, and was having it delivered next-day.
I had him order part number 7981K82 on pg. 530 (Autotuning P-I-D Temperature Controllers with Fuzzy Logic, the mini one with solid state relay voltage output) and part number 7456K14 on pg. 873 (Long-Life Medium-Amp Relays, with 3-30 VAC/VDC control voltage).
Then I got an old electrical box of some sort, a standard light switch, and a big ass heat sink (a regular ass heat sink would work fine as well, but my partner just happened to have a big assed one he was willing to give me
). I milled holes in the box for the temp. controller and switch, and a hole that would allow me to bolt the heat sink to the outside of the box with the relay (which is bolted to the heat sink) on the inside.
Then the next day the stuff came and I wired it up and installed it. It works great.
BTW, McMaster doesn't list the brand name of the controller in their catalog, but it's Fuji, in case you're interested. Also, I decided to stick with the thermocouple that was already in the oven; it seemed in just fine condition. (K-type - chromel/alumel)
edit: The light switch isn't necessary. It's just handy to be able to turn the power off to the oven instantly with the flick of a switch, rather than trying to navigate through the menus on the controller or having to unplug it.