Well, this blew apart before I could even find time to get involved!
The support plates are the ones on the front caliper that reach across the rotor to contact both brake pads, and on the rear caliper they appear to support each end on the inner pads only. The front ones are not available individually, but you can get them as part of the fitting kit, which does both calipers:
04947-17010 - $22.71 - Fitting kit, front
On the rear, the outer pads take anti-rattle clips on their ends. If you do need an anti-rattle clip for the rear, we can still get them. The lower ones are no. 2 and the upper ones are no. 1, or you can get the fitting kit, which appears to have all four pieces for each caliper (total eight pieces).
47748-14050 - $4.07 - Spring, anti-rattle, no. 1
47743-14040 - $4.07 - spring, anti-rattle, no. 2
04948-17030 - $12.13 - Fitting kit, rear