I'd be surprised if any Scuba shop wouldn't refill it. My buddy had to get his airbag filled in Seattle last year after flying in from Denver. I think the first place he went to did it.
Curious as to when it blows. Are there parts that have to be replaced? For BCA I believe there is an O Ring part that has to be swapped out. For the Mammut System, there is a burst plate. Mystery Ranch have any of that?