Stuck rear brake pin/slider

My rear pads are wearing very unevenly and it looks like the drivers side pin is getting stuck in the back. Do I need to replace or lube it? Where do I get the pin and or what do I lube it with? I'll replace the pads at the same time.

I had a pin stuck on my front brakes last time I serviced them. In my case it was a rubber bushing around the pin that had swelled sticking it into the bore. I was able to pick up a Hardware kit from my local auto-parts store that contained new pins, new rubber bushings. I would assume they would sell the same hardware kits for the rear. Hope this helps!