I have several methods, one is the USB on the bike,, although this is also used for Apple Car Play with the phone.....
There is also a 12vdc socket I use with a USB adapter as an alternate....
In my tank bag I carry a powerbank, one of two I have,. a high capacity one which will do several charges and another that would do a couple.
I also use the power bank to charge my second Sena intercom battery in the tank bag.
My iPhone 12 mini charge goes down quickly if not plugged in, mostly due to it being bluetoothed to the Satnav if not connected to the bike for Apple Car play.....