If you don't find earplugs just get some cotton wool to stuff into your ear. If you make sure that both ears have equally big self-made earplugs so that the sound isn't louder on one side. Compared to cheap, not reusable earplugs cotton wool actually takes less higher frequencies away, which results in better overall sound. (Otherwise the bass and the drums are all you hear if the mix isn't top notch).
When you've got time and money order some earplugs via the internet. Decent ones you can reuse will only cost you about 20 - 30$ and they hold for a few years if you take care of them. You can also go to a local shop that sells "high-end" earplugs, which don't take away the high frequencies at all and just make it quieter, without changing the sound (or at least not badly). However, those will cost you 200 $ if you get lucky and probably more.