I don't know if this is something you would want to use on your bag, and do wait for others' advice, but they do have "sweater stones". These are pumice stones shaped so that when you run them over fabric, they remove pills and refresh the fabric. I know they are nice for sweaters and other clothing, but I have no idea if they are advisable for bags. If anything, I would only use it if the pilling gets worse somewhere down the road.
Or also they have those little D-Fuzz It combs..those work well, I use them on my sweaters