The two current importers that I know of, of Walther products, are Walther Arms, and Earl from ERS. Neither of them have this trigger available. The fact that they could bring them over, but choose not to, says a lot. I don't think you understand how dangerous this trigger makes this pistol. A FTRB malfunction could result in a KB with the pistol firing out of battery. The pistol can easily go full-auto (I won't explain how so please don't ask). A drop from 18" high, or an impact from the rear could result in a discharge. Etc.
My suggestion would be to go with any other aftermarket trigger for these pistols. All of the alternatives available come with a drop safety on the trigger, and do not depress the firing pin block.