Rear bumper - inner plastic lining

I got rear-ended by a hit & run driver (relatively slow speed, and we were all ok), and my rear bumper is now hanging down on the left side.
I picked up some black plastic that fell off, a roughly 5" wide piece broken in two, which it turns out was attached to the inside of the bumper, and exactly the very plastic which slides over the bracket, and on which the bumper hangs.

Now I could search for entire bumpers, but I really only want that inside liner piece. Is this possible to get separate?

Thank much for your time!

I would post a link to the relevant section on Jaguar Classic Parts but you haven’t told us what year & model you have. Add that information to your signature in your profile.

1995 XJR
I believe from avatar

Sorry, yes, it’s a 1995 XJR 4.0 supercharged.
And thanks for posting that link to the rear bumper section, I think I have the energy absorbing type:

But this parts list doesn’t show or mention the plastic liner that is riveted to the bumper, and without it the bumper cannot slide over the Guide Block (#12 in the schematic).

I just bought these pieces on Ebay. The seller cut off their rivets from the bumper, and described them as:
“Rear bumper support plastic both pieces: BEC19910, BEC19911”.
I assume these are OEM numbers embossed in the plastic parts, as I cannot find anything online about them.