I've been looking for my HG lime colour as well. As others have suggested, Chartreuse [the shimmery pigment, not the matte] is good.. can turn up a bit yellow, depending on the lighting, though. I've also heard that chartreuse over a lucky green shadestick is really good.. haven't yet tried it, though.
Also, mark from Avon has a colour called "Dragonfly" that is a nice lime green.. but its staying power isn't exactly what I'd like.