timbuk2 messenger bags make a few pad choices ? not sure if they are velcro over ? but I would just search for something like that ? otherwise often places that can do sewing can work on webbing and make your straps have nice buckle ends to take on or off put on other straps etc.. for cheap
Sewing shop can put on some rubberized/suede strip (check Michaels or Jo Ann stores) on the bottom of your strap and this should help - at least it does for my Lowepro EX 160 which was designed with it.