A guy I knew back in South Africa had a gun chambered in Walther 9x18. He could never find ammo for it, but got good results by shortening 9x19 cases to 9x18 and reloading. He also found that he could shoot .380 ACP ammo, relying on the extractor to hold the cartridge against the breechface - but I don't recommend this, for obvious reasons of safety. I suspect reloading with shortened cases will be the way to go (or you could talk to a specialty ammo loader, such as our own WESHOOT, to have them load 500 or 1,000 rounds for you - but if they have to shorten the cases as well, the cost will be very high, I'm afraid).