I need a place that can add some heavy duty snaps to a pair of gaiters.

Is there a repair/alterations place in the Salt Lake area that specializes in repairing or modifying outdoor gear and clothing?

Perhaps you have a handy friend with one of these?
http://www.rei.com/product/602099

I used to make most of my gear and still have some of the snap-setting kits. I found it useful to put a bit of flexible urethane on the cloth before the final set (e.g. seam grip nowadays), to decrease the chance of rip-out and ravel of threads. You can hasten the curing time of the urethane by wetting the cloth after the snap is fully set.

Good luck.

Check Kirkman's at 3100 south and State. I've gotten stuff repaired there before.

Second Kirkhams. I've never had anything done there, but I've heard good things from a friend of mine.