I got mine from
www.filterbagS.com. The customer service is awesome and you get a discount after so many peices (20 or 25 I think). I have dealt with both places and liked filterbags.com better. Ask for Ginny.
Also, go for the Nylon monofilment mesh bags, they last way longer than the polyester ones. FWIW, I got NMO100P4POSS
http://www.filterbags.com/filter_bag_pricing.htm
If you want the 7" ers, NMO100P1POSS would be perfect.
HTH