You may luck out & find a good used one. I'd check it or have it checked for Clutch wear before buying tho'. Probably best to buy new.
Stay away from the Gov Lock Carriers, their Ok for mild use, no burn outs etc.. they tend to break parts when going from dirt to pavement while spinning etc..
An Eaton Posi, Eaton/Detroit TrueTrac or Yukon Dura Grip would work well.
Auburn Posi Carriers aren't rebuildable, they use metal cones inplace of Clutch Plates like the Eaton & Yukon DuraGrip "Eaton Copy" use.
Carriers types, ID Pics >> http://rides.webshots.com/album/55410292AnMJrE
Courtesy of "BigGearHead"