Search for "camera insert" on Amazon and pick one that can fit in what space is left in your messenger bag, then see if it has enough compartments. Crumpler's haven is relatively slim (the Medium and Small sizes are meant for the cam to go in one way, unlike others that are wider if not square-ish), plus it has pockets for SDcards. I have two in my BBP Industries Messenger instead of their own rectangular insert - the rounder flanks on the Crumpler inserts keeps the bag from bulging too much or having that corner bulge, plus I got more one more divider - enough separate compartments to fit a Fuji X100, WCL-X100 wide converter, all chargers (laptop brick, Fuji and Caseology chargers holding spare batteries), and an Aurisonics IEM in an Otterbox without scratching up the cam or its converter lens. If you're not lugging a camera like I am then even just one Haven can fit whatever you want inside, assuming it fits in your messenger bag.