You're right. Any sabot slug is hard to come by right now. 20 gauge is spotty, but 12 gauge is nearly impossible to find. I've got a box or two of Federal Premiums BRI type slugs that shoot well out of my Ithaca M37 with rifled Deerslayer barrel, and a decent quantity of Hornady SST slugs that print 1 inch at 100 yards out of my Savage 212. And I've got a metric ton of Federal and Remington 1 oz foster slugs that shoot very well out of my other Ithaca M37 with 26" vent rib barrel with a IC choke tube. I can hit stationary clays with that gun with foster slugs at 75 yards, which is plenty accurate enough.

Too bad about the chipped antler. That's not bad, though, and gives you something to point to when someone sees it on your wall.