You'll have to search around a bit, maybe find someone near you on here who breeds their own rodents. I'm no expert, so others may be able to give you better advice, but I would suggest finding appropriately sized live mice just to get him eating regularly again. Once he's taken a few regular live feedings you can try f/t (same size) mice, probably giving the mouse a little "zombie dance". This worked for me when I rescued my male who had been on live mice the entire 4 years of his life. Then when switching from f/t mice to f/t rats, I scented the rats with mice a few times.Hope this helps a bit..
Edit: Also, I might add, I've heard some people say they've had BPs who simply refuse to ever switch from live to f/t. So, consider that as well.