This actually makes me wonder. I know there are vaginal and oral onaholes out there but is there anything for paizuri?
There are entire sex-dolls, but they are rather expensive and hard to maintain. Also you can buy just a torso with boobs and vagina. Or oversized oppai pad, as Tsuchino mentioned higher.
Japan's inventions in terms of masturbation devices are pretty spectacular and surprising, but it's expensive fun.