So I found myself reading up on the Monkey Rocker, and it said that it was compatible with almost any dildo due to having an attachment for Vac-U-Lock as well as a "large rubber O-rings for almost any flared dildo".
https://www.monkeyrocker.com/oringmountfinal.jpg
Does a similar device exist with a suction cup? As in - a suction cup accessory for any dildo!