It seems that there is a new holsterish thing that does not cover the trigger guard coming to market every week. Most of them are terrible. A few, like some of the clips that attach to the handgun, aren’t terrible but should still make you a bit nervous due to the exposed trigger guard. I generally recommend carrying with a proper, full-coverage holster but if you insist on something other than that please consider using something like the Trigger Guard Holster from Black Rhino Concealment (BRC).
BRC makes the Trigger Guard Holster for a number of common firearms. It snaps onto the trigger guard, completely covering it and adding only minimal bulk to the overall size of the handgun. To use it with something like a handgun clip you would simply hitch the short static cord on your belt. The static cord quickly reaches the extent of its length during the draw stroke which automatically removes the Trigger Guard Holster from the handgun. It can also be used without a clip in the same manner.
These types of holsters are actually handy for a number of storage and carry uses. Check out the Trigger Guard Holsters at Black Rhino Concealment.