Honestly if I were to make a wing shooting gun I would build it with a set of recessed breech Manton lock castings from TRS then build a recessed Nock breech for it. Have good springs, mainspring at least, made for the lock and maybe face the frizzen and see how it sparks.
While the Nock is not the fastest breech according to Larry Pletcher it IS the most consistent.
And consistency is key in wing shooting.
But the most consistent flintlock I have ever shot is my 16 bore rifle made as described here. And its not at all slow either. It has very strong springs and gives descent flint life and never needs knapping, when the flint stops sparking its invariably a waste of time to do other than change it out.
But you get what you pay for. But getting one for $1000? In the white or otherwise this is not likely. Building the lock from castings, making it right, then making a hooked, recessed Nock breech from bar stock? This is worth 700-800 on its own.
Dan