hi buddy
i use a guntuff
http://www.jsramsbottom.com/products/rangefinders/gtlrf-guntuff-laser-rangefinder-18---400-yard--meter-[cr2-battery-included].html
but i think the price has gone up?
i got mine for £89.95
any ways you don't necessary need one for calibrating your mildot,s
all you have to do is measure out from 8yds/mtrs to 45yds/mtrs and place a target at each 8,10,15,20,25,30,35,40,45 distance.then zero at 30yds if .22 and 35yds .177 fill your rifle up to 170bar and take a shot at each target and make a note(mental,paper) and then you have calibrated your scope to