I'm not 100% sure on the Greensmoke, I think they might be proprietary, or at least an oddball offshoot of the KR808 standard, hopefully someone with experience on that brand can chime in.
V2 Cigs uses the KR808D-1 standard. Many vendors carry cartos and accessories that are compatible. Have a look at the vendor list here on the ECF for starters.
Forum Suppliers List