With the OrfosPro, you could connect all lights on each bicycle to one powerbank.
https://www.orfos.us/pages/pro
So the capacity of the powerbank decides about the runtime.
And you can get an 4x18650 powerbank with 4x3,5A cells (50Wh).
Soshine E3S-QC 18650x4 Portable Power Source Bank + Quick Charger 30W - Soshine
Soshine High Quality E3S 18650 Portable Best Power Bank+Charger 3.5A - Soshine