It's been awhile for me, but the actual swivel seats available always took up too much room to really swivel side-to-side in the canoe. I was most often looking for lower back support, and I know there are several options out there, including a "sling back" cushion that hooked on the front of the seat and allowed the person to lean back into it. I didn't find them all that comfortable.
The most practicable option for extended cruising for me was just a plain old boat cushion.
Raising your center of gravity in a tippy boat is rarely a good idea, but some canoes are quite wide and may still be fairly stable.
The light-weight "racing" canoes have butt-holding seats, curved to fit your bottom. You can often find these sold separately. They are not cushioned, however.
If you paddle alone, consider sitting in the front seat, facing the stern. This gives you more stability and control, you are less likely to have the bow swing, or become a sail when the winds pick up.
Be safe, have fun.