According to the JMate article, a company called Genyo produced this as a “shoulder massager” in 1997. The design was approved by Sanrio, the owner of Hello Kitty. The item was not officially intended for any “adult” purposes, but of course people quickly put the vibrating thing to other uses. By 1999 it had become a cult item in Japanese porn movies. Sanrio was less than happy, and eventually found an excuse to seize and destroy the molds.

This means that you’re probably out of luck if you want one of these, but it seems they are sometimes auctioned on eBay.