Here is something that I've been waiting for someone more skilled to make... but I decided, hey, why not do it myself? :D
These pictures are emulated off of the style of ones I've seen in person (a psychiatrist I have shares office space with the biggest hearing clinic in my region).
I think that the lack of modern hearing aids for our sims is a bit silly. They're as common as glasses and I know many people who wear them happily. These particular hearing aids are found in the Blush section for all ages, in five colours - light, medium, dark, black, and white, for all types of sims. They fit over your sim's ear and are detailed as heck!
I tried my best to emulate my friend's hearing aids as hers go over her entire ear and not just the canal, because of Bluetooth capability for using her phone and tablet with. They are stylish and hard to notice unless you look closely - just like a real hearing aid.
I hope that you find use in these! :D