It can be done, but your biggest hurdle will be finding a lock to fit in the mortice. The drum can be pulled, and replaced with a touch hole liner, that will be the easy part. The Track of the Wolf catalog has full size pic's of the parts they sell. You can trace the mortice, and try and match it, as close as posible. You could also get a Chambers gun builders lock, which has a large rectangular plate you could shape, but it has a Germanic pan and wouldn't look right on that style gun in my opinion, but even that can be reworked if you are up to it. Bottom line is it can be done, but may be more work than you wish to take on.
Bill