HELP with electric wheelchair charger

Hi everyone, can anyone give me some advise please, i live in west wales and i'm going to london in oct to see a show, my first time back for 40 years, anyway im going in my electric wheelchair, it goes for 6 miles without recharge i think, anyway as im staying in london 2 nights i can only carry 1 bag,  and my things i need will be in it, how can i take the charger ? is there anywhere i could get a charger like the red cross to use for 1 night?i would be greatfull for any advise