You may have good luck finding one from a stock carver's web site. I didn't even think of it when I came to do mine. I put a new (and nicely figured) piece of wood on my Colt Lightning too, but kept the crescent butt plate shape. i simply lengthened the LOP, and since this increased the height of the butt plate, I found an early Hawken repro plate and modified it to resemble my Winchester butt plate. After it was polished, I rust blued it and it came out very nicely.
I have a sense that these butt stocks were made for people of different stature, or perhaps shooting style, than we of this period. I'm about 6' 1 1/2" tall with 35" inseams and a long neck, so that little butt stock on each rifle wasn't working for me. The '76 in particular has a lot of drop in the comb, and that coupled with the short butt stock, made my shooting awkward to say the least. It felt like my face was sort of floating all over the place, and it was difficult to get a serious hold on the rifle. The '76's new butt stock has a shotgun style now, and I simply took the crescent out of the butt rather than deliberately trying to make it longer. Now it is solid on the shoulder, and my cheek has an anchor. Can't wait to give it a try.
Thanks again for the kind words.