Standard KR808D-1 cartomizers. Libertyflights, vaporsetc, NHaler. NHaler has a bunch of different 808 cartos -- I might pick up some of their G5 clearomizers to try, for kicks. Not sure who vapor4life is using now, but their 3.4 ohm coolcarts are nice at higher voltage (or if you prefer a cooler vape on the Volt), and their Wow cartos are supposed to be decent too (all the vapor4life stuff is KR808D-1, same fitting as the Volt).
Coupon codes are october20 for LF, vapezone (IIRC) for vaporsetc, SAVEINNJ for NHaler. Check the PIF Deals and Steals thread for whatever the latest vapor4life code is.