At the risk of sounding grumpier than I really am -- it's understood that the "half-moon" rubber is not original. The question though is where to get the half-moon rubber bumper.
I'm curious too. I couldn't care less what was original. I like the half-moon much better than the original style trim, and the guys who have dashes with that pad need a source for it in the event that they need a repair, etc.