Get one of these: https://www.costco.com/p/-/infinity-x1-7000l-dual-po...

Costco UK stocks them at £23+VAT. You have a good high power torch and a Power bank in one.

I have one which I keep in my work bag but which only gets used sparingly usually when allocated a work van with a duff radio and I have to fall back on my JBL Bluetooth speaker which needs plugging in to last over a whole shift - I prefer not to use the van's USB power socket with its frequent OFF/ON cycles as the van is turned off and on. Still shows as fully charged though one of the blue charging state lights doesn't work any more but it is the one which indicated a quarter charged so not a real issue.