I have two very different options for you. The first and cheapest is a big jumbo box of Howard Leight plugs from amazon. They work great and at that bulk price you can have a couple pairs in each jacket or pant or trunk or wherever. The second is earbuds called Riderx1 from a company call eaos. They fit under a helmet and offer great sound reduction (I think better than the highly rated ear plugs) with the added bonus of having tunes. They are kinda pricey but worth it in my book, pretty good sound and a mic for calls also.
Edit: I just realized you are only talking about ones with sound, sorry about that. The rider x1's might be something for you to try then.
2015 CBR1000RR YR-250
1999 ZRX1100 Eddie Lawson
1984 Goldwing Aspencade (WIP bought after a light deer smashing)
1983 LTD550 (WIP cafe project for friends to ride)