SharkBite 1/2-in Pex Barb x 1/4-in Od Compression Brass Quarter Turn Supply in the Shut-Off Valves department at Lowes.com
Connect PEX to Copper, Replace Copper with PEX | SharkBite
SHARKBITE PEX-only plumbing system | Supply House Times
SharkBite 3/4 Inch x 3/4 Inch x 1/2 Inch Reducing Tee, Pack of 6, Push To Connect Brass Plumbing Fitting, PEX Pipe, Copper, CPVC, PE-RT, HDPE, U412LF - Faucet Parts And Attachments - Amazon.com
Pro-tip: Thinking of using Pex-A? Avoid Sharkbite (brand) brass fittings (found at some Lowes). The tiny shoulders make it next to impossible to get a proper fit on 90's and Tee's. :
Pex/Sharkbite Bypass Assembly (28311) 3/4" | Inspect USA
SharkBite 1/2-Inch End Cap, Push-to-Connect, PEX, Copper, CPVC - Walmart.com