Tons of ways to get there with a DIY option.
Here's the current incarnation after Manfrotto started marketing the design.
http://services.manfrotto.com/figrig/
PVC is fine, though sometimes it is easier to smoothly balance an object with some weight to it. Never used one of these, so no idea if that is relevant with the camera weight in the center.
Focus on one of these would definitely require some trickery for DSLR. Works great if you can get a deep stop and not worry about pulls. Otherwise some sort of follow gear on a whip is probably the cheapest option. Even then you would need one hell of a hand to avoid tweaking the camera around while pulling. There's a great DIY dslr follow focus on the web someplace made from basically a rollerblading wheel and some spare plastic. It's linked around here someplace, but a quick google should find it fairly easily too.
Thoughts:
Salvage a steering wheel from an RV or semi-truck?
Look around for objects with bases made of metal hoops and salvage one of those? Lamps, Chairs, coffee tables, etc. I'd stay away from anything with a chrome finish, even if I had a sandblaster it would still probably be a waste of time to remove the finish to get to workable metal.
Get an old brake rotor, some strong clamps, a sturdy table, some metal pipe or tube, and a torch. Then bend one. It can be done, and since you aren't building something to bear a substantial load, the heat stress during the bends shouldn't be an issue. Weld in the center bracing, paint to your liking and slap some padding on the handles.
Might be interesting to try this with a machined rim from a mountain bike - though sort of a spendy object to use.
There are probably more sources where one could salvage a lightweight metal or durable plastic hoop; just none coming to mind at the moment.