So I'm working on my brother's '86 T/A, replacing the rear rotors/calipers/pads (all stock, had a hell of a time removing the rotors)

The calipers do not have hollow pistons, they have are the screw in type, so the appropriate pads are flat (no retaining clips sticking out). Thing is, one of the inner pads has a shiny metal disk-like piece on it that clips onto the pad and holds the pad to the caliper.

What's this piece called and, more importantly, where can I get one? The new pads have a metal clip riveted to the back that I'll have to grind off to get the pads to fit, I'd like to get the metal piece for both sides as well, although one side was installed without it.

 

Assume these are the iron calipers. Afaik, at least on mine, there were no shims or clips on the rear pads. The pad has a little **** that sticks out, and engages with a slot in the piston head. The trick is getting the piston retracted, whilst maintaining the slot in the perpendicular direction to line up with the pad ****.

Last set of pads I got for the rears had that clip too - used for the front pistons (same pads for front or rear). Just pull it off and discard it.