Look at the lock inside the door - if it's a S & G Group 2 you can replace it with a mechanical (dial) combination (still S&G Groups 2). The locking mechanism is the same size (at least it was on mine). Might want to make sure the hole in the door (that the wire currently goes thru from the keyboard) is big enough for the shaft on the dial. Take some pictures of the inside of the lock and go talk to a safe locksmith (I've worked with Harmon's Safe & Lock in Mesa). They'll steer you in the right direction.
My safe originally had a mechanical dial, then I changed it to a digital, then back to mechanical for the same reason as your concern.
good luck