Amazon.com: 20Pack 1/2 Inch PVC Nipple Male Thread Coupling Adapter Connector (Male x Male) 1/2" PVC NPT Male Thread Coupling Pipe Fitting for Thread plumbing Pipe, Home or Industrial Use, Schedule 40 :
PVC Threaded Coupler - DripWorks
Thrifco Plumbing 8113823 1/2 Inch Threaded x Threaded SCH 40 PVC Coupling (White) - Walmart.com
HydroMaxx 1/2-in Schedule 40 PVC Male Adapter Connector Conduit Fittings (150-Pack) in the Conduit Fittings department at Lowes.com