I use plugs made for musicians from etymotic research.
www.etymotic.com
Your local audiologist makes a form cast of your ears from which custom fit plugs are made. I use the 15 db filters. (They have 9 and 25, too)
I suffer from tinnitus after years of games and working at a radio station ("DJ ear"). I used the foam plugs for years but I found I couldn't hear the players. The plugs filter out the crowd noise, the whistle, but not the coaches. My interaction with players and coaches has increased and has helped my overall game.
And they're deductible! $150/
pr.
Our game Saturday, I blew the whistle for the first time and OOPS! Had forgotten to put them in. Man, that whistle is LOUD.