As far as I can see, there isn't one. At least not shown in any of the Parts manuals. I checked mine and don't see any kind of bumper either. The only thing the manuals show is a bumper for the 64-65 Chevelle, Group 4.603, P/N 3846500 - Bumper, Parking Brake.
If there WAS one used on the Camaro, it wasn't serviced separately.
Ed