So you have YOKE reg and DIN tank valve. You should be able to find the threaded insert that goes into a DIN valve allowing a YOKE reg to attach and work just fine. Some valves actually come with the insert - I have one, but it's DIN 200. If your tank is DIN300, then you need to check out some on-line dive shops and get one. It will NOT be $100-120, but should be A LOT less.
Cheers,
-S