In the early days there were some tanks with smaller threaded necks, and finding a DIN for those is probably a problem... but anything manufactured today for SCUBA is gonna have the right neck.
OMS and Scuba Pro (and I'm sure others, but these are two I own) make 225 BAR DIN valves that have inserts for use with yoke regs, so you can use either. Of the two I recommend the Scuba pro - more expensive but much smoother, higher quality valves. Unless you're using HP tanks the 225 BAR are fine and offer the advantage of being able to use the Yoke.
Rick