this ones great cause it has fast charging.
https://www.amazon.com/gp/product/B078FTSJWJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
youll need a sae connector too
I'd recomend getting a waterproof wireless charger and sealing every connection with silicone.
I just attached an iphone cable at first, and with just a drop of water it will bust the cable, and or drain the battery.
I also occasionally had starting issues, so i cleaned my terminals and put vaseline all over them, but just in case, I removed the running light from the headlight housing, snipped the cables, and ran the usb to that. This way it turns on and off automatically when the bike does.
I had the idea when I decided to replace the notoriously crappy plastic lamp with a glass one, and got one without a spot for the running light bulb by mistake.
happy mistake
https://www.amazon.com/gp/product/B001OMEPEU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
while you are at it, upgrading to led bulb makes as much difference as replacing the lamp, and don't skimp on that part. The led has to be made to project the light exactly as the original bulb did within the lamp.
I settled on this one after trying the cheapos:
https://www.amazon.com/gp/product/B079K4P1R9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I feel LEDs are the way to go. They last long, use less power, and are brighter. The ones on that site look over priced and what about returns? Amazon has free returns.
I bought these for $19 each at the time which are up to $24: https://www.amazon.com/gp/product/B001OMEPEU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 and these bulbs . They are glass and look nice. The Hella were my second choice but are more money $36 but have rounded fronts: https://www.amazon.com/Hella-002395031-HLMP-165MM-ECE/dp/B005OULUQO/ref=psdc_318323011_t1_B001OMEPEU
Also got these bulbs for $38 which went down to 36: https://www.amazon.com/gp/product/B09HS7499B/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 . They are extremely bright and use heatsinks instead of fans for longer life. Also these do not come with a decoder chip for newer cars which I did not need and would worry that would be a point of falure. I was thinking of using a PWM to lower the brightness on the low beams because they are a bit bright on a dim roads but good on well lit roads. The high beams are perfect.