I found a pair of these a couple of weeks ago (for a little less than retail). Apparently designed for running, but they do actually work on a bike.

https://nightrunner270.com/



USB rechargeable (with a nice split cable). Pretty bright on the front. They have 3 modes, low, high, and flash. Since the pedals rotate, I use them on low. Adjustable angle. The hold in pretty well on the bike, but I've knocked them off a couple of times when walking (I suppose I didn't read the instructions about tying them on). So far nothing broken.

After an hour or two, they start flashing the rear light as a low light indicator, but they seem to continue working at least an hour or so after beginning to flash.

Ads indicate that the new model and more expensive lasts longer.

I suppose my biggest concern is minimal rear lighting. Otherwise, they seem to be a good augment to other cycling lights, assuming one has shoelaces.