I've had a few drop leg holsters, and they all suffer from wobble when you're running. Even the more stable platforms like Serpa will have some.
My personal recommendation for a holster is the
4.0 SEALS Special Operations Holster. It's made by Eagle Industries and is a real-steel product and is available in OD, black, CB, khaki, and for $10 more, genuine multicam.
It's the most stable drop leg holster I've ever seen, and it's universal. It'll fit anything from a tiny Glock 26 to a hand cannon like the Desert Eagle with or without tactical accessories like flashlights and lasers. I can easily even fit my Mac 11 in it, and despite the long protruding magazine, it doesn't wobble in the slightest while running.