The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
But what about a lock mechanism? Most are framelocks, which may not work.Flipper???
Does it have to be a locking knife? Maybe a slipjoint or friction folder would be more suitable for someone without full use of their thumb? There are models with an extended tang like the Higonokami which helps keep the knife open.
Alternatively perhaps the OP could use a flipper knife and simply close the knife two handed, operating the frame or linerlock with his opposite thumb.