Suggestions for a small waterproof bag to hold 2 lenses and camera

I do a lot of kayaking and always bring my XSi w/ the Tamron 18-270. Right now it basically goes in a big ziplock with a towel wrapped around it.

Is there a small bag made that's waterproof that would hold this set-up plus another lens like the Sigma 10-20?

I thought I saw some bag that is worn like a backpack except it goes on your chest. Can't remember who made it though.

Any suggestions?

Thanks

I think Ortleib makes something like that: