I struggle with hypermobility myself. I've got some K-Tape and what I do is wrap it around my joints to keep them steady. You can get some in CVS or online. I've learnt to put it on with some YouTube tutorials there's plenty! It stays on for about a week so it's very convenient as I don't have to be changing it all the time.
Hope this helps!
One thing one of our riders did was change to flexible stirrups for her hyper-mobility. Additionally, there are polyurethane inserts for boots to help alleviate pain and reduce swelling in joints. EquiTape can also help during pre-ride, during or post-rides to help or "train" your hyper-motion. Hope that helps!