A Remington Rolling Block butt plate might also work. The magazines are hard to find. I have had two and one was incomplete.
It took many years to find the first one.
I'm beginning to notice that... I reached out to that gentleman you referred me to, but he never wrote me back.
I'm hoping the Baltimore antique gun show has one somewhere hidden in tbe stacks.
I'll try to find a Rolling block buttplate. Thanks for the advice!