Longines sei tacche waterproof crown

Hi all! Looking for an early unsigned Longines waterproof crown c. 1940s in steel. It is for an early Longines waterproof tank (pictured), which were originally fitted with crowns very similar to what was found on the first generation sei tacche watches (example also pictured)

There is a tap size difference (1.2mm on 6Ts vs. 0.9mm for this 25.17 movement), but I’ll entertain any aesthetically correct crown - I can have a stem custom made.

Thanks for the space OF!

Juergen