They will have them but you may have to screw two parts together. You need a hose thread to 1/4" adapter like used to screw a pressure gauge on to a hose bib or garden hose, probably brass which is OK, and a 1/4" MIP x John Guest Speed Fit adapter which will be plastic. Maybe $5 total?
They sell an all plastic one with the Guest adapter which is a fine thread that fits your faucet.You will have to remove the screen and then screw it on by hand.Should be able to find it in the plumbing dept or go to the household ro systems and ask the helpfull Lowe's emplyoee.Brass is bad in my book ha ha ha