Those are still in use? The department I used to be on had four (I think) and they are all junk. Well, not totally junk, they'd work, but fall apart VERY easily. Especially the one assigned to my dad. It would continuously fall apart. The Chief's radio would keep messing up internally, and the other two were just as bad.
Hopefully they replace those soon with more like the Relm's in "Big Red".
But, to answer your question, try calling your local Motorola dealer, or eBay.