A lot of holster manufacturers (particularly those who produce leather holsters) won't touch pistol with a light for that reason. Using a thumb break is a reasonable way around the issue. As blasphemous as it sounds kydex generally is easier to get a retention point on with a light.
I'm a big fan of JM Custom Kydex but I don't see a 1911 + light combo on his site. Maybe @policemedic can share some wisdom.
This is kinda/sorta necroposting (though nowhere near as bad as a case study), but for whatever reason I just saw this.
I'm a big user of kydex holsters. In fact, the only leather ones I have are my Crossbreed (which is only the backer) and my ankle holster for my BUG.
Wilson Combat markets a kydex holster specifically for 1911s with the TLR6. In fact, I'd wager most good kydex makers could hook @Marauder06 up.