This should work for ya...
Edit,
Unless your connecting to pex tubing. Or dont have a threaded fitting to thread into.
John Guest 3/8 in. O.D. x 1/2 in. MIP NPTF Polypropylene Push-to-Connect Adapter Fitting 803229 - The Home Depot
The John Guest 3/8 in. O.D. x 1/2 in. NPTF Push-to-Connect Male Connector is manufactured from white polypropylene and equipped with EPDM O-rings utilizing John Guest's push-fit technology to make an easy, reliable, leak-free connection. Developed to satisfy a wide range of applications it can...
www.homedepot.com
Edit,
Unless your connecting to pex tubing. Or dont have a threaded fitting to thread into.