Even if a GP can legally rx you bupe for off-label use I seriously doubt you would find one who would be willing to do so. Asking a doc (especially one you don't have a history with) for a specific strong opiate without it being your usual med is the best way to get shown the door and treated like a junky, doctors prescribe for you , you don't prescribe for yourself.
It's your body and whatnot but tha'ts just how it works.
Best thing you can do is find a good regular GP, build up a bit of a relationship and then you can start discussing treatment issues involving controlled drugs.