I ordered this Mountainsmith Rolling Zip Top Tote once and sent it back because it was too big. It's 15 x 26 x 15, maybe something like this would work? They also make ones without wheels and travel cubes that fit inside that may help organize other things.

http://tinyurl.com/ywnddj

You might also look at soft sided coolers. They're still somewhat padded and usually lighter weight than camera bags. There are some with wheels and backpack ones.

http://tinyurl.com/5cpenh