Brass, 3/8 in x 1/8 in Fitting Pipe Size, Reducing Adapter - 1DFY6|6-2 RA-B - Grainger
Brass Male To Female Pipe Fitting BSP Thread Extension Connectors 1/8" 1/4" 3/8" | eBay
Union 1/8 NPT-M To 1/8 NPT-M, Brass - MHOxygen
1/8 IP x 3/16", Both Ends Threaded, Fixture Stem - Lamp Pipe, Your Choice of Lengths from 1-1/2" to 36" (1/8 IP = 3/8" diameter) (22249BU) - Antique Lamp Supply - Quality Lamp Parts Since 1952