tanith
There are gadgets that lower into a bath but how successful they are I dont know.
Yes you can get a complete support Cushion type seat that gets pumped up and then lowered in to the bath, I had one for my partner. However we found he got really cold when we emptied the bath and he had to wait for the cushion to raise to the top of the bath before he could get out. He only used it a couple of times before we sold it on. There is also a hard seat, where you get lowered in to the bath and reverse, but I would think the issue would be the same. Have you thought of a walk in bath, would that be the answer to your problem. I love my bath and would hate to have to do without one.