Did a quick search, but came up dry. Anyone had any success in finding an inexpensive rear disc brake adapter that is compatible with a 1999 Specialized Stumpjumper FSR-XC Pro? My son recently bought a used Mavic UST 3.01 disk wheel set and used Avid mechanical disk brake set. Unfortunately, we couldn’t mount the rear brake to the swing arm given the lack of IS mounting holes. Do we have any inexpensive options?