I am not aware of any current-production taillights that are designed around user-replaceable Li-Ion batteries.
There's the Lupine Rotlicht Max. USB rechargeable - ✓ User replaceable lithium-polymer battery - ✓
https://www.lupinenorthamerica.com/p...t-accessories/
Note: you will pay dearly for the USB charging over Tourist in MSN's remove-and-charge AA or AAA taillights.