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.
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.