dont know of any usb rechargable but I got a 5v for $40 that uses 14500 battys.
mod box from cybervex
he also has the bartleby for 50.00 that does recharge at 3.7 by usb. this is one great mod if you want 3,7. uses 1- 14500 batty
pm cybervex for info on his mod..
great mod. and the price cant be beat..
Check out alsolv from greatlakesvapor..