Part 27 here but sadly out of stock
https://www.gunpartscorp.com/gun-man...s-walther/lp53
Maybe someone could measure the size and thread of a cap for you Vic?
You may strike lucky with a cap off something else-----maybe a S2 pistol or similar? Im pretty sure someone on here would be prepared to make to a simple threaded cap and you could sort out a guide that is separate to the cap.
Maybe if you know the thread, someone may know of a nut or something that fits something else-------wheel nut or pipe fitting etc?