I use 3M ClearE-A-R (UF01021), they're transparent and cost about 3€ for a reusable, washable pair on Amazon Germany. It does change the sound but I think that's inevitable (EDIT: for this price range, at least)
I would not say it's inevitable. As a musician, I use Elacin filters with custom moulds, and these are great. There is no noticeable change in the sound itself, you just hear the sound at lower volume and more clearly, without most of the echoes.
These are pricey though (around 200 EUR), but definitely cheaper than hearing loss.
I've also used he Etymotic "ETY Plugs" which are more expensive (about $12/pair) but are designed for flat frequency pass-through. They give moderate sound reduction without changing the sound.
These are the earplugs I used. I'm not sure if there are better or worse out there. The price point was low enough that I just bought them without a lot of research and they worked perfectly.
