Here's a weird suggestion: I got one of these back massagers. I had a bum-orgasm once with this. I had to use it fairly rigorously to get the desired result. I could hold this and not have to curl myself up and twist to thrust another kind of toy. I didn't think it was worth the trouble, and I only achieved it once. I didn't want to wreck my rectum.
Fun feature: You can use any of the ends. I also managed to jam a bigger toy on one of them.