It must go inside the pants, be made of kydex, have belt loops, and have a thumb break.  

Compac C-T.A.C. ?

ctac doesn't have a thumb break, but the weapon does snap into place and is held by a dimple through the trigger guard.

i don't know that i've seen a kydex holster with a thumb break, not saying it doesn't exist, just not familiar.  most people that go iwb (like myself) rely on belt tension to hold the weapon in place.  the ctac is a good choice though- i carry a sig 226 in mine.

good luck.

The comp-tac c-tac is tension adjustable and found at www.comp-tac.com.  I don't know of anyone who doesn't like this holster including me.   IWB's/Kydex with thumbreak?  Maybe someone else can help.  good luck