Powerful search tool on this forum--lots of good info on brakes. The casing number on the calipers should lead your repair shop to the local NAPA or truck parts store. With few exceptions, there is really no such thing as "Alpine parts." For example: the axle assembly is Meritor--used on many vehicles besides Alpine. Am sure someone will chime in with specific part numbers. Would be a bit concerned that the repair shop was stymied so easily with this.
PS--the tech library on the ACA website is also a great source of information, a quick search of the forum pointed to Bosch truck parts....
2003 40' MDTS
Garden Ridge, Texas