I finally remembered to check mine and while I can't seem to find a pic online, its kind of like this one:


This is a bad angle of the gasket attachment because from the other side, you can see how it's got multiple hooks on which to attach the 'gasket' and this gives you a more customized fit. It's stretchy, too...

The one I had opened at the back like a regular wedge, but this one looks like it might even work better with the bottles behind it.

I bought mine (also Avenir like the photo) at D1ck's Sporting Goods about 3 years ago for all of $9.99. Sorry that I can't be of more help!