No there are lots of different threadings.
What is the diameter of the battery - less than 9mm or slightly over 9mm? If under 9mm forget it.
If over 9mm...
If the battery has male protruding threads and the cartomizer has recessed female threads, and KR808D-1 (Nebula) cartos do not fit, then either try KR808D-2 cartos (Greensmoke or blanks from Vaporkings.com or AZSMokeFree.com) OR INSTEAD try a D2 to D1 adapter from LeCig.com (if that adapter works then you could use your Nebula cartos)
If the battery has recessed threads and the cartomizer has male protruding threads then it is most likely RN4081 threading or 510 threading. You could either try two 99 cent adapters from Goodprophets (510 to 808. and 4081 to 808 - or they may say 510 to KR808D-1 and 4081 to KR808D-1) and see if either of those makes your Nebula cartos work on it. OR you could first buy some RN4081 cartos (SmokeStik Hendu,
njoy Npro, Njoy 2-n-1 at some 7-11's) and if they don't work then try Boge 510 3 ohm (standard resistance) blank cartomizers (or you can find some prefilled 510 cartos at LiquidXpress and Chinese
juice ones at Vaporkings.com)
None of the above is guaranteed to work because some ripoff rebranders purposely use models that are incompatible with anything. Also - if 510 threading works, it does not mean he has a 510. Never stick his battery in a 510 charger. There are multiple models with 510 threading and some are reverse electrical polarity.
If you need to find something locally, check VaporSearchUSA.com
And IMO - just treat this as a stop-gap and have him get something decent, popular and compatible.