Air Hose for Pneumatic Tools 1/4 in. Male x 3/8 in. Female Brass Pipe Reducer Coupler Connector Fitting 150 PSI Maximum 1/4 in 18 NPT Home Garage or Professional Shop: Amazon.com: Industrial & Scientific
3/8 in x 1/4 in Fitting Size, Female x Male, Hydraulic Hose Adapter - 52JF78|3/8 X 1/4 PTR-SS - Grainger
Amazon.com: Legines 1/4" NPT Male to 3/8" Barb Fitting, Brass Barbed Adapter Straight Connector 2 pcs : Industrial & Scientific
Ideal Vacuum | Adapter 3/8 inch hose barb to 1/4 inch ID Male NPT, Stainless Steel, Vacuum Fittings Adapter, Swagelok, SS-6-HC-1-4
Brass Hose BSP End Connector Barb Adapter Pipe Air Gas 1/8" 1" 1 /4"3/8 1/2" 3/4" | eBay