I think you're making a big mistake if you don't use ear plugs. I wear them all the time. I buy the by the hundreds. I use them for lots of stuff - motorcycle, lawnmower, metal work, etc.
Anyway, there's two things to look for. Obviously, you want the one with the highest decible rating. The dB scale is logorithmic. 30 is twice as loud as 29, and 31 is twice as loud as 30.
Second, they have to fit, and fit well. That really is the key. You end up trying a few different ones until you find what works for ya. I'v tried all kinds, even custom molded ones. I like these:
Max Earplugs (10 pairs) - Whitehorse Gear