I just finished a job doing that very thing. McKenzie Taxidermy Supply handles imitation European horn mount skulls by Tab Hinton.
They have both "sloted" skulls for your situation and Pedical skulls for sheds.
They come for white tails, mule deer, moose, elk, caribou and antelope skulls. They also have a foam panel that looks good.
They run from $33 for wgite tail to $100 for the moose.
You trim the skull cap to fit the cut out, glue in place and then blend with epoxie skulp and paint to match.
They came out way better than I was expecting and well worth the time and cost.

Thanks Bon, that sounds pretty good! I'll talk to a few taxidermists and see if they could make it happen that way.
Regards-Don.