I also run the harbor freight gun, I ended up getting it for 50$ with a coupon. Im working on 2 ovens right now, one for doing small parts and one for doing big parts, wheels, motorcycle frames, handpoles, etc,etc.
For the small oven, I am using a old cheap tool box I had, It one of those wal mart brand cabinet box, I used the bottom chest of it, and a little toaster oven that my wife wanted to replace, It's not a toaster. But its the little counter top oven thing, It had 4 heating elements in it and a timer and thermostat, everything you need for a powder coating oven. Iv already got the elements in place and all wired up. Im still working on a hinge for the door, and I think Im gonna use the glass door from the oven and put a window and a oven light in it so I can keep a eye on things.
I'll put some pics up when I finish it up.