Vapcell and the nitecore batteries seem to be popular for rechargeable lithiums. Sounds like coast may have some new batteries as well.
I am planning on switching everything over to a cr123 style headlamp (hmr50) and having an extra battery serving double duty in my flextail zero pump. I would love to find a cr123 cell that supports discharge via usb-c to charge a phone battery in a pinch too.
I think nitecore currently has the highest advertised capacity cr123 size at 950mah.
USB-C Rechargeable 16340 Battery From Nitecore's most recent battery update, the NL169R is a high-quality 16340 Lithium-ion USB-C rechargeable battery. It has increased its capacity 950mAh by an impressive 46%, compared to its predecessor, the NL166. The NL169R also features a light indicator...
nitecorestore.com