Nipple size for antique Belgian Double Barrel

[Jdlc433]

I have an 11 gauge double barrel shotgun made in Belgium. It's a pretty solid example and I am wanting to shoot it.
The right nipple is in good condition but the left is mangled.
Where would I find replacement nipples for this.
I'm not sure of the thread size but the outside diameter of the threads is .262 on my micrometer.
Any ideas on how I could obtain a new set of nipples for this gun?

 

[Supercracker]

I also have an original Belgian that I shoot. the threads seemed....."ok". But just to be sure I got some oversized nipples and taps from TOW. Ran the OS tap through and the OS nipple fits like new.


One suggestion. The OS nipples aren't marked that I can find. SO buy 2 or 3 sets and put the extras in a baggy labeled with the size along with the tap/. That way in 2 years when you need new nipples and can't remember the size you'll have what you need.