Depending on the type of pants, I've been using a Don Hume pocket holster for the 27. When the pants won't support that heavy a gun, I'm forced to the Galco Cop Ankle Glove. I know you mentioned that it doesn't work with your pants. Perhaps another brand might work better?
Galco is also making a tuckable appendix holster for that model, that might hide decently well in dress clothes.
http://www.usgalco.com/HolsterPG3.as...=1756&GunID=50
I have been wearing my jacket in the office lately. That serves perfectly well to hide the Glock in the little cheap $10 Glock Sport Holster. It's actually quite nice.