There are a lot more than Sticky and Bulldog out there. It looks like Fobus
is making an ankle holster (several, actually).
Academy lists a few dozen different ankle holsters from several big name makers, but there aren't a lot of reviews on them. Safariland and Galco both have good reputations for duty gear, so if you're planning on carrying it for work, you might look at one from them, like the Safariland/
Bianchi Negotiator.
The main things you probably want to look at are that it stays in place without moving around and that it's comfortable. A loaded doublestack .40 like the G27 is going to be blockier and heavier compared to something like a J-Frame or a singlestack 9mm or .380. If you're going to be doing a lot of moving around like walking a beat or chasing someone, there are models that have an extra calf strap to help keep it where it belongs.