I use the etymotic "etykids". I think they're exactly the same as the MC5 buds, except their maximum volume is limited to a lower level. And trust me, the maximum volume on these is more than anyone should really need.
I got them over the MC5s because they were cheaper. I was at first worried about the phones being physically smaller than the MC5s... I figured since they were marketed for kids, they'd be smaller to fit into kids' ears, but that's not the case. I wear a size XL helmet, and these seal in my ear just fine. They isolate sound very well.
Here's a link.
http://www.amazon.com/Etymotic-Research-EREK-5-BLACK-Safe-Listening-Headset-/dp/B005TOV0OM/ref=sr_1_1?s=electronics&ie=UTF8&qid=1342062461&sr=1-1&keywords=ety+kids
I got them over the MC5s because they were cheaper. I was at first worried about the phones being physically smaller than the MC5s... I figured since they were marketed for kids, they'd be smaller to fit into kids' ears, but that's not the case. I wear a size XL helmet, and these seal in my ear just fine. They isolate sound very well.
Here's a link.