Take a look at the GI issue Trigger Finger Mittens. I just picked up a pair for a CO elk hunt later this year and I believe they are going to work well. You don't have to pull off your glove to shoot but, you can tuck your trigger finger in and out the mitten when needed. I bought a pair larger than I needed so I can wear them over regular gloves. They seem to be well made and they are cheap.
