You might try to contact Randy's Hunting Center in Bad Axe, MI. That was ground zero for slug glun hunters before the .450 Bushmaster came along. They might be able to help with finding a quantity of Lightfields.
I looked though my targets and I did have decent luck with Rem Core-Loct Ultra. I'd start with the heaviest slug you can find if the Lightfields are gone forever.
That really stinks! I had one one of those A-Bolts and it was awesome with the Lightfield Hybred EXPs. Sure am glad I was able to move it. I did not have nearly as good of luck with the lighter sabots.
50 yard group.