Man IDK, Black Currant has a pretty unique flavor profile. I suppose you could sub Bilberry (FA), not really the same. But it would give you an added dark berry to the mix.
I can't believe I haven't rated this. This is fantastic. My husband requests it regularly. I did substitute the black currant with Nic Vape Dark Raz initially because I didn't have the black currant but I was so happy with the juice that I bought a bottle so I could try it as published. Thanks for sharing Mark!