Again, if I was a bank that used these safes, I would not only epoxy the USB ports but also instruct the people picking up the money from them to inspect the epoxy. Think of it like the seal on an envelope. Apply the epoxy, mix in some glitter or something so it has a unique pattern, and take a photo of the epoxied port at time of application. Compare pictures when picking up the money. It won't keep attackers out, but it will let you know if somebody got in.

This is a less than perfect solution, of course. The manufacturer of these safes deserves all of the flack it gets for not fixing the vulnerability /tout suite/. If I remember the article correctly, they've known about the attack for a year!!!