I bought 4 day Bumpy's and a wool one from Kellys Closet but had to return all of them. The wool (SUPER large ) Bumpy didn't fit around my son's huge thighs. The wool one has velcro and a couple of snaps and I couldn't even get a snap snapped and they dug into my son's thighs. The day Bumpys were great except for the fact that the velcro on the wings/tabs tore up my son's thighs.
Anyhow.. Kelly's Closet has free shipping and the prices seem comparable..at least on the Bumpy's.
My Bumpy's fit fine over ME OS so you should be fine there. I "think" I got mine from naturalbabies.com but I don't recall as it was ages ago. I love them though and haven't had much chance to use them as DD potty trained right after they arrived.