Why don't you just enjoy the model you bought? Long ago, I bought an NJoy and liked it very much. You indicate you like it also. Many posters harangue anyone who has something different from the 510 EGO or KR808. Don't buy into it. Yours is a good one too. Later, you will want to buy another model, but there is no perfect e cig. There is nothing wrong with what you have now. Buy some liquids from Backwoods Brew or KickBass Vapor to refill; find a cheaper place to buy carts, batteries, and atomizers, and enjoy what you already have. If you have the two piece NJoy, you can buy cartomizers here,
All in one cartomizer for RN4081 (Njoy NPRO or SmokingEverywhere Gold) electronic cigarette If you don't have the two piece, then there is sure to be an adapter to allow you to use cartomizers. The difference between the NJoy with cartomizers and KR808 is simply being 2 rather than 3 pieces. Some people prefer the atomizer your unit uses over the 510 atomizers, so perhaps you already have something better.