I use the Army issue mechanics tool bag in nylon duck canvas. You can find them occasionally at surplus stores. Wrap web handles, serious YKK zipper, and double bottom that stays flat and wraps up to make two pockets inside.
It's built to hold as much steel in it as you can tote around.
A quick google search will get you vendors for Jack Bauer's go bag, along with Blackhawk, Eagle, TAD, and a dozen others.
Countycomm offers different bags by Maratac, in a variety of sizes, with exterior MOLLE webbing. Lots of shooters use them, too, along with uses for First Response, call out, or emergency gear for vehicles.
Some of the electricians and carpenters bags work well, and they can be found at flea markets or pawn shops. You can also find well padded laptop backpacks at college resale shops, too.