I'll second that ^ ^ ^ ^ ^
And to be clear, when I agreed that the OP might try a live "appetizer", that's an option that's debatable...you hate to regress, but it often does work.
When I kept BPs, I also raised rodents, so easy availability (& variety) was always there, but it isn't ideal for many keepers, & depending on the size/age
of the BP, this refusal may have nothing to do with the vet visit at all. He's most likely just being a typical BP. (It's also why I love my rat snakes, lol...)