These guys had every replacement part I needed to rebuild my entire braking system on my MC trailer last summer. Replacing the master, and shock absorber is a PITA btw... I believe you can buy the whole swing away assembly, and I would recommend doing that as opposed to rebuilding it yourself. You want to open all your bleeders on the calipers and pump brake cleaner throughout the system.
Good luck!
http://www.spectrac.com/