I bought a box of 200 sets from a web site (I don't remember which one) for about $20 plus S&H about a year ago. I got Howard Leight brand "Max Lite." They're foam, bullit-shaped, and last a long time. I use them for commuting, swimming, and sleeping. You can get them with or without neck cord.

Do a search on "howard leight" & Max Lite"