The best purchase, apart from the various canonical equipment, including vibrators etc., was a set of wooden clothes pegs.
Wood, even when wet, never slips, unlike rubber.
I dismantled a vibrating dildo, one of the small format ones, like those for clitus, so to speak, and I took the motor.
With a good amount of hot glue, I soldered it to the central part of the spring, then I applied two long, soft tassel ribbons to the sides, so that I could keep the clothespin in place, tying it to the girl's hips.
You can easily apply the clip on the clitoral hood or when possible, directly on the clitoris, if your partner tolerates it well. The result is very satisfactory.
I still have to solve the problem of the power cables which, although they are thin, require particular attention. I partly solved the problem by attaching the battery and switch to one thigh, with a very elegant garter...