How and why were you feeding your snake gerbils if you don't want it to eat gerbil? Bps should only be fed whatever you are not afraid to feed it the rest of their lives. They are picky picky picky.
How hard have you tried to switch beavis back to rats or mice, (rats are cheaper in the end when he is large)? If they do not eat a rat the first time you offer, don't give up, offer a gerbil and try next week. Just don't feed them for a week or two and try again. Yes, you can try scenting, and there are all kinds of other ways to try and get him switched, but you gotta be patient. I had a king snake that did not eat for almost 5 months while I was switching him over from live to f/t. Depending on the size of your bp, it can go up to a year not eating, so don't be afraid to miss a meal or 10.
Best of luck.