USB->Bluetooth/other RF->USB?

I'm getting sick of cable clutter. I use a keyboard podium and the keyboard cable keeps getting caught under the wheels. I love my wireless trackball for not having that problem.

I don't want to buy a new keyboard. I like my keyboard. I do want to eliminate the cable getting in the way, though.

It seems like the obvious solution is a battery-powered dongle I can plug the keyboard into that turns it into a Bluetooth device. An alternative that used some proprietary RF signalling would work just fine too, however.

When I started writing this I was going to admit that my searching skills were failing me, but I have in fact discovered "USB extenders", all with prices well over $100, that look like they might do the trick, although the ones I'm seeing require wall power, which would rather defeat the purpose. With all the things we can put into a dongle inexpensively, I'd think this would be out there.

Anybody know of a device like what I'm looking for in not-ridiculously-expensive? Or of something close to what I'm looking for that might be adaptable to the purpose?