Not that I'm personally any more expert in the matter than you, ER, but I do know that the Ben Wa Effect is achieved through the combination of motion of the, uh, "host body" and the constantly varying effects of gravity upon the implements. In zero-g they'd just sit there inert, like a...well, I won't go there.

I understand, though, that there are deluxe versions of the device which are hollow and partially-filled with mercury. The idea is to enhance the motion with the irregular sloshing about of the mercury, and possibly even in microgravity, an astronaut moving around might generate sufficient sloshing to experience a shadow of the intended effect.

All in all, I'd say there are simpler ways to achieve the intended outcome in space. Especially with a mixed crew, if'n ya know what I mean. Ask the NASA flight surgeons about that one.