Amazon.com: Legines 1/2" NPT Female to 3/8" NPT Male Reducing Pipe Adapter Brass Reducer Coupling Fitting 1200psi High Pressure (Pack of 2) : Industrial & Scientific
1/2 to 3/8 Reducer Faucet Adapter - Compression Brass Pipe Fitting, 3/8 Male to 1/2 Male Supply Line Adapter for RV Kitchen Plumbing, Water Hose Pipe Connector with Rubber Washer, (2 Pack) - Amazon.com
1/2" Male SAE Flare X 3/8" Female SAE Flare | MB Sturgis