Thought I would test my theory on the bumper caps as well.
For some reason ( that someone here may be aware of ) - every Stern cap appears to be available as a repro except these 

Hey Wotto

I asked PBR about them around 18 months ago.  They said they had 1 cap in stock, and no plans to do another run. 

Interesting that your switches around the big flipper are red.  Mine are white.  However, I have seen both before, so figure was just a matter of what was in the parts bin at the time :)