Turning out that I may not need one. I have all the pieces, but it's about a 1,000 piece jigsaw puzzle. It's going back together OK with some quickset epoxy. Once I get it back to the basic form, I'll get a fiberglass kit and put a skin over it to give it a bit more structure and to finish and paint. Thinking of using a can of household insulating foam underneath to fill the voids and give it some support for vibration.
These plastic bumpers and covers are more about appearance and don't have much strength to begin with, so I'm not too concerned there.
Beats $125 and a six hour drive to get a replacement that still would have to be painted.
Not sure how fiberglass and resin will adhere to the flexible plastic skin. I think body shops do use or have a flexible bondo to fix even a minor groove. I super glued a side mirror housing on my Xterra and it is still good after ten years and it was in pieces but not flexible. I once painted a flex bumper on a 75 Firebird and it needed a flex additive added to the paint. Maybe it isn't needed these days.