Jim Chamber, and L&R make a variety of left-handed locks. So does Caywood, and Davis. You can link up to their websites by going back to the index page on this forum, scroll up to " Member Resources", and then look for an entry, " Articles, Charts, and Links". Click on " Links" and it will take you to a long list of suppliers. Several General Suppliers, such as Track of the Wolf, sell many of these locks, and provide you with full-sized pictures of each which makes it easier to compare with the size gun you are working on.
I have a Tennessee Poor Boy style rifle acquired more than 30 years ago, from a now Bankrupt company. I ordered it with a Cochran lock in LH percussion, then had it converted to Flintlock a few years later. Cochran is no longer in business, and the closest size lock that would fit my gun today would be a large Siler, sold by Jim Chambers. My gun is .50 caliber. There was a time when Dixie Gun Works sold similar rifles in a variety of calibers, from .32 to .50. If you are building a smaller gun for a child or woman, or man of short stature, in a small bore caliber, you might want to downsize the parts, including the lock, and look for a small Siler, or pistol lock to use on the small gun. All this has to do with how the lock parts( internal) fit up against the barrel of the gun, with the biggest issue being whether the lock is Long enough to reach from behind the breech plug to where you need the Touch Hole located.
Good luck on your build. :hatsoff: