I recently got this Apace Vision usb rechargeable tail light and I couldn't be happier.
https://www.amazon.com/Apace-Vision-...s=apace+vision
It's bright and the charge lasts a long time. I do night commutes once/week and it's been on my bike for a month and it's still going strong. I'd definitely get another.
PBSF's and others taught me that changing batteries is a PITA.