Everbilt 1/4 in. OD Compression x 1/2 in. FIP Brass Adapter Fitting 801029 - The Home Depot
Amazon.com: Universal Vacuum Hose Adapter 2-1/2 Inch to 1-1/4 Inch,1-1/4 Inch to 1-3/8 Inch to 1-1/2 Inch,1-3/8 Inch to 1-1/4 Inch Wet Dry Vacuum Converter Reducer Attachment Adapter kit for Vacuum Cleaner(6pcs) :
3/4" Male x 1/4" Female NPT Hex Bushing Adapter Pipe Reducer Brass Fit – compressor-source