I have a Joseph Manton from the 1830's, and a Henry Egg 1850's. Both have a metal end piece. I do have a picture of the fore end and fitting on the Henry Egg. (No idea how to post it, but I think I could e-mail it to you.) As I remember, the basic set up is similar to the Pedersoli reproduction, which might make a reasonable pattern starting point. I'm not home so I can't check on this right now. Pedersoli parts can be purchased from flintlocksetc.com.
You might also find useful photos on the "Roosevelt and Drake" site.