GD,
now might be a great time to get a cast done of the chamber & slug you bore!
As Kuduae has put it, you may own a very rare bird indeed & to have your rifle's dimensions proven it will be a great help for him & others to verify what you really need!
And yes it will be a rare treat for all us to see your rifle speak once again.

Woodleigh bullets do make a .440" projectile of 401gn in weight - Part No 67.
http://www.woodleighbullets.com.au/
Bertram brass certainly do make more than a few odd sized cases, including the 11.2x72 Schuler - again your chamber cast will verify what you can then use or what to modify to get you going.

The link below is an American contact point - worth a try I guess after you work out your chamber.
https://bertrambrass.com/contact-us/

Keep at it mate, we're all behind you on this.
93x64mm