Get the Howard Leight Max earplugs. 200 pairs is $20. As far as I am aware they are the highest NRR ear protection you can find. They get an amazing seal. I do a ton of competition shooting and used to get headaches after matches but have not had any issues since switching to these. I suggest pairing them with some basic electronic earmuffs like the Howard Leight Impact Sports or Pros. Adding muffs only adds 2-3 Db reduction, but muffs help a lot of concussion, which you'll want indoors.

Hearing only goes one way so it is extremely important to protect it with the best offerings available. The super expensive electronic ear pro are often worse at actually protecting your hearing and are also much easier to unintentionally break the seal on. Highest rated muffs I am aware of are the Howard Leight Pros, which have a NRR of 30, but again, NRR doesn't stack linearly.

If you are going to be by the speakers and need even more protection, try the Howard Leight MAX-1. I bought a box of 200 a few years ago and still have half a box left (I use them for motorcycle riding). They're $20 right now on amazon and NRR 30 rated.

http://www.amazon.com/Howard-Leight-Earplugs-Uncorded-NRR33/dp/B0013A0C0Y

Howard Leight MAX-1 Uncorded NR33 Foam Earplugs Box, 200 Pair (Orange) https://smile.amazon.com/dp/B0013A0C0Y/ref=cm_sw_r_cp_api_glc_fabc_9gp9FbTENT1KX

These are awesome Howard Leight MAX-1 Uncorded NR33... https://www.amazon.com/dp/B0013A0C0Y?ref=ppx_pop_mob_ap_share