I’m sure you can buy something that improves hearing that uses headphones rather than anything in the ear.
Many years ago a friend of mine had a Sony Walkman that had the optional facility to amplify the surrounding sound (rather than play a tape) – which could have doubled as a hearing aid.
It might make you look hip, walking around with people thinking that you are listening to music – when actually you can hear everything they say (and converse with them).
As with most things in life the more you pay the better the quality – so reckon on paying at least £20 for a quality product.