What 85lc said, not monometal, but In Australia for a while we could buy the Sellier & Bellot 196gr .318 bullet (No.2941) in boxes of 100 for ~50 bucks a box, about 35USD. Standard cup'n'core soft-nose design. I bought a few boxes just to have on the shelf.

Feel compelled to add that I don't rate S&B brass very highly, having had issues with reloading .303 Brit and 7mm Mauser in the distant past, but I have shot a bunch of their bullets in 8mm Mauser, 196-grain SPCE (No.2945), and they seem to work just fine.

Unless you really need monometal, it might be worth contacting the S&B importer and ask the question.

Hendo:
Have you checked the dimensions of the chamber neck in your Type B Mauser?
I was given excellent advice on bullets for my example by kuduae in this thread from 2018. Seems you may be able to shoot .323 projectiles in your .318-bore if the chamber has been necked/throated for the larger projectile. Worth checking...