Troy - I'd check tackofthewolf.com for locks - of the English variety.

I would NOT use an Italian lock. I've never seen one that appeared to have been made well. They were all very rough inside and needed too much work to make work properly, ie: CVA or Pedersoli. The L&R locks are quite good - I have several and they all suit me just fine - flint or percussion.

If making a large single in flint in earlier style, the large Queen Anne rounded lock plate would work nicely, I think. There are several that would "fit" the subject.