I’d never seen this bike light setup before, and have to say, it’s quite ingenious. It appears to have a single 18650 and a built in usb charging port, and 100% waterproof. The cool thing about it is, it comes with a thin plate that you zip-tie to your seat post and the light sticks on that plate with strong magnets. So when you need to recharge, yank it off and take it inside and plug it into a usb charger.
They are a little bit pricey, but see what you think. I think they may be worth it if you’re on a bike a lot.
These would also be handy to have in your car in case you break down at night. Stick one on the trunk lid of your car and put it on flashing mode.
Here’s the link
(yes, that is the correct domain name)