Hi B.,
I haven't checked other people's responses yet - I hope I'm not repeating anything they've already said!
I hope this link works:
http://www.toysrus.com/entry.jsp?source=PE&entry=2267259
I bought this online from Babies-R-Us, and I've been very happy with it. The print on mine is different than this one, but it's the same product.
It works on both shopping carts & high chairs, and it has loops that you can hook little toys on (so you don't have to keep picking them off the floor - something each of us is pretty good at, I'm sure!!) as well as a little pocket for a few of your items (wallet or cell phone). It covers pretty much all the parts that your little one could touch or try to eat, and it has a strap that attaches to the shopping cart to avoid any falls (I haven't figured out how to strap him into a high chair with it, but it doesn't seem like it'd be easy for him to fall out of that). It also can be "mushed" up into a small carrying bag that is attached. I've been really happy with this, and I've definitely gotten a lot of use out of it.
There's another one that I'd been looking at before I bought this one; it's called the Baby Buggy Bag. I decided against it because it was a bit more expensive (@$60); there are several stores online that sell them if you did a search.
I hope this helps!