I can't find any device on the market at that time. In fact the first device to market seems to have been in 1993, a few years before the SheWee.

However, there are two parents of interest in the right time period:

https://patents.google.com/patent/US3177500A/en

https://patents.google.com/patent/US3964111A/en

The second, from 1975 has the exact purpose as the SheWee, and it's patent expiration of 1993 coincides with such products hitting the market. It's theoretically possible the original inventor sold some small scale in the decades between 1975 and 1993, and the sudden adoption when the patent expires shows there was intetest, but no way to prove it that I can find.