Hey Janis,
The 12 on the 15x1 needles the lady pulled out was the size of the needle, not the type. You're looking for a "type" of needle. If they try to sell you a needle clearly labeled as a 15x1 as a 12x1, go talk to someone else in the store. That's like trying to put a car tire on a truck. Yes, they use similar numbers, but they're not for the same usage.
Cathy, thanks for the clarification on the aliases of the DBx1 needles. I have 4 packages of Groz-Beckert needles here, they have all sorts of numbers on them but no DBx1 so I thought I would have to order some, but they did say: 135x7, 134, 135x5, 1738, 16x257(which told me they may work), 16x231, SY 1955, 797, Sy1901, Sy 1903, DPx7.