What parts do you need?
The only real specialty part is the porcelin socket. There are plenty of theatrical supplier swthat will sell replacement sockets for pars. Depending on how your particular par is put together these are easily replaced with either a screw driver or a wire splice.
Again depending on your par pop rivets, bolts, nuts, thumb screws... all pretty common. If you get stuck look for specialty screw or hardware suppliers. Out here we have a chain called Tacoma Screw which sells all sorts of specialty items. If you get stuck or can't find a local supplier try McMaster Carr. They offer incredible online hardware shopping and service.
Again depending on how much you pay for pars you might repair them... or want to recycle them.
