I'd buy the lock that's closest, and patch the hole cut by the inletting machine, let in the preferred lock. Of course once you patch the hole, any appropriate lock should fit up.
Personally, I have a Nock, Roller Ketland, Roller Manton (L&R externals), L&R Manton, & Durs Egg-one in use, the others on deck. That gives you an idea of what i like in TN-style locks. I'd not hesitate to try a Chambers Classic Ketland either.
TOW's life-sized pics may help you match things up. You can do tracings* or photocopies to compare. You might just have to patch the back end a little. You don't have to fill the whole void, just a good substantial "slab" up top.
So many originals were/are converted/reconverted or repaired/patched that a decent job of patching up and re-inletting will impress folks more than a "drop-in" fit. Maybe some folks "in-the-know" will understand right off the bat, and be thankful of your diligence. I know it would impress me. Patching holes is a stockwood-working fundamental, as my first stock taught me (over and over).
Have at it, show 'em what you can learn and do!
*remembering "typing paper" and how we did all that tracing as kids...wonder if they make that anymore?