Thanks to a friendly CPF'er, I've acquired both of the holsters that come with the Inova X5 and the Pelican M6. Both work well with the L4, but in different ways. The Pelican one is bigger and will work better for frequent in-and-out use -- as it's stiff, has a snap top, and has ample room for the L4. It's also about a half-inch too long on the height of the top loop-over, and is too deep by a slightly lesser amount. Meanwhile, the X5 holster is a snug, stretchy fit -- but perhaps a bit too much so, as there's a bit of a struggle to get it in or out, especially wrestling with the L4's clip.
Overall, the Pelican holster is the winner, if only because it's generously sized on the L4, which is better than being too small.
I still am not sure if I'm the "holster type", but intend to give it a try to make it easier to carry the L4 more places without chewing up the other contents of my pocket.
Hope this is helpful,
Dave