I get your point about the phone life. Seems on that RM thought their fans phones would be ok !.
Surely if your ticket was on your phone you would take care of the battery. The same as if a paper ticket was in my wallet.
If you have spent hundreds of pounds on tickets, travel etc than getting a cheap charging pack would break the bank.
I'm not sure how to go about all that shit myself and I'm being honest. Also unless you've got accomodation booked you'd be one of thousands scrambling about trying to find a charging point.