Check out Cheaperndirt and Major's Surplus, they will have a number of items that are PALS/MOLLE supporting. Keep in mind that a lot of people, if you say PALS webbing, will have no idea, but the same guys know MOLLE.

Also check out SpecOps Brand's THE Pack. It's pricy for me, but not to freakishly far out of reach. I just have three backpacks in that size right now, and I can't justify another. <img src="/images/graemlins/smile.gif" alt="" />

Also, try ebay. There are a bunch of e-stores with shop fronts there that sell MOLLE-compatable backpacks.