The gunmaker's lock kit is just a Siler or delux Siler with a square plate, and is going to be pretty small...You could use the internals on a largely scratchbuilt lock, though. I think most of those doglocks had no internal bridle (or were even actually type 2 English locks with a lateral sear rather than true flintlock), but since no one is going to see the inside you could include the bridle if you wanted.
Sad thing is, there just isn't much in the way of musket-sized locks available commercially, and if you want one you have to either put up with the Rifle Shoppe (whose parts aren't even necessarily useable), use one of the handful of locks/parts sets available elsewhere (Track of the Wolf, J. Brooks, Indian-or Italian-made spares), or make your own.