Ever have an itch that you can't seem to scratch, even if you can reach it? I have (no wise cracks). I found the solution...I have a threaded rod that is part of a picture framing clamp, that works great. Of course, one must not permit it to move over the skin across the threads, or it will likely abrade the skin, but that isn't necessary if applying the right amount of pressure, and only moving it as much as the skin will stretch. If moving in the same direction as the threads, then abrasion isn't much of a problem, unless you get carried away.
I believe that any threaded rod, such as one might find in a hardware store will work, as that rod diameter is not critical. As for thread size, one would just have to experment, as that wider/deeper threads could be a problem, or might work better...I don't know.
As for anyone that thinks that this is an odd topic for the Chillout Room, I thought that it needed a more useful purpose than just playing games.