check lowes or Home Depot, in the section with small tubing adaptors usually near the place with the PVC pipe
you may need to pick up a fitting that goes from the faucet to a 1/4" threaded pipe fitting (NPT) then add another fitting that goes from the 1/4" (NPT) to tubing. make sure you have teh right tubing outside diameter (OD)
You might try Elliotts Hardware. They have everything and are usually much better at helping that the Big Box guys. You might pay a little more but at least you wont be standing in aisle 31 wondering where the adapters are, and finally finding them on an endcap of aisle 6 35 minutes later after not being able to find a soul would look liked they worked there!
Not at all positive, but I thought the Elliots in Grapevine closed. Call to be sure. The other one is near Downtown Dallas (near Wycliff/Motor Street and Harry Hines Blvd) and in Richardson/Plano off Coit Rd between Park and Parker.