I will mention that the shaft diameter on the DBx1 needle varies from brand to brand. You may have to try a few to get the right ones. I can use the DBx1 needles I seem to find here in my 12 and 13 "clones" but only if I dremel the shafts down to fit. It's tedious and if you shave too much on the wrong side, it can cause clearance issues. If you can find some locally that fit (take the head with you) - get the brand and then order in bulk online. What I do know is that the Gros Beckert DBx1 needles that I have here have a large shaft, so they're not especially suitable.
This thread here:
http://www.quiltingboard.com/vintage...ml#post5986789 has a lot of information in it (in various posts from Mizkaki) about DBx1 needles and it's all worth reading.