M.K.
Hi L.,
I used to work in a home for developmentally disabled adults and lots of them had ear problems. We used to use some soft moldable silicone earplugs for bathing and they seemed to work pretty good. You can work them into shape to cover the ear canal. They are reusable until they get yucky. We used to just buy them at the pharmacy and you can order them online (just do a google search for "silicone earplugs").
Good Luck,
M.