I asked about bitcoin banknotes in the past and some people obviously didn't like that. There can exist bitcoin banknotes issued by some entity (state) that the state can promise to redeem in real bitcoin... And if this solves a real problem, such things will appear despite the extreme hate from some people in this community (like ecash is gaining steam despite the extreme hate... guys, if you want ecash to die, solve the problem it solves instead of insulting people developing or using it).

But I am wondering something very simple in your case. Couldn't you just ask the venue for a charger to connect your phone to and make the payment?