Powering gps

[Cox76y]

Hi all,
Currently I have a gps mounted to the handlebars on my 2018 and connected to the headlight wiring. I thought this would be enough power to charge the gps which has an inbuilt battery whilst I am riding. This is not the case however as it uses more power than the charge current from the lighting provides.
Just wondering if I put a switch in the circuit to turn the headlight off does anyone know if this would mean that more power would then be available to charge the gps. I really don't want to run it straight off the battery as I am already having starter issues and don't want to add additional current draw directly to the battery.
Any help n advice would be appreciated.
Thanks
Jc