Three-wheeled e-bikes (trikes) also exist. I know someone who also has balance issue (mid 40’s with reduced motor control on one side of the body) who uses one all the time.

They are also used a lot by elderly people who are afraid to fall over. A friend of mine’s mother uses one for that reason. Depending on your needs they come with either a normal bicycle saddle or even a full seat if you need the extra support.