I once tried to read the back threads on LED headlights. I found that almost every LED kit link on Amazon was a dead link. Since some kits are probably total junk, or don't work well with the Leaf, it seems like a better place would be a Wiki page listing the "current favorite" kits of the Leaf owner community.
With my ICE truck, I bought someone else's LED headlamps. Er, LED bulbs in halogen lenses. Big mistake. It's not necessarily a simple plug and play. Incandescent bulb mirrors work differently than LED reflectors. My LED lights gave me little "on the road" light and blinded everyone. I could sure read street signs but not see the pothole at the pole's base. I took the LEDs out and reinstalled my halogens.
If you proceed with an Amazon purchase, make sure your LED light kits are SAE compliant.