River Rock 1AA 1W Luxeon body is compatible with the Fenix L1D / L2D head (kind of).

Yes, the Fenix LxD head works with the RR 1AA / Nuwai X1. Just remove the two corrugated copper rings from the head of the RR and put them into the LxD head. There seems to be a slight contact problem as the threads of the RR body are anodized, the copper rings solve this albeit not too effectively. Use additional pieces of aluminum foil to improve the contact. I pretty much just bought myself an extra 1AA LxD body with an extra RR head for $20.00. Not sure if the RR head fits on an LxD body, I tried but it won't fit in with light pressure and twisting.