I didn't know they made them for this market so I bought a little battery powered fish tank pump a couple of years ago and use it sometimes...but in Texas where the ambient summer temp is near 100F anyway, it isn't very efficient. So I resorted to ice in ziplock bags. I run it up and down the barrel and press it against the receiver under the scope on each side for 30 sec (total) or so and then let the remaining heat of the barrel redistribute evenly for a minute. That gets it to well below 100F and I'm good to go again for 2 - 3 shots. I don't care if people look at me funny...it works better/faster than air.