Non-Lethal Pellets

I just sent a note to Jester about his non-lethal pellets and the idea of making them out of melted wax also looks good. But, I do not have a low-power air gun to use at close range to pop the squirrels that raid the bird feeders under the eve of our house. I know nothing about low-power air guns to use at close range. ~20 feet.
Any recommendations?