Me too! What a great idea and great look! I assume the Fat Boy is a 3.7V?
Manufacturer specification
Full charge -Blue led 4.2v
Low battery warning- Red led 3.3v
Auto shut down-2.8v
I can personally confirm that the Fatboy operates at 4.2 volts fully charged and am currently using it with a 1.7ohm smoktech carto without problem.
The parent company appears to be Dubacco under D&B enterprises out of South Korea according to Alibaba listings.
dubaccoDOTtrustpass.alibabaDOTcom/
Says a FatBoy 2 VV is coming soon which should be sold at a very reasonable pricepoint.
Mopar at Canvape would know more.