3/8 FPT x 1/4" MPT, Brass Pipe Adapter - Hi-Line Inc.
CRAFTSMAN 1/4-in to 3/8-in Socket Adapter in the Socket Adapters department at Lowes.com
Amazon.com : Camera Screw Adapter Thread 1/4" Male to 3/8" Female and 3/8" Male to 1/4" Female Adapter Set for Camera Monitor, Tripod, Mount : Electronics
D.169RJ) -Compact Adapter (1/4>3/8)
BrassCraft 3/8-in x 1/4-in Threaded Adapter Fitting in the Brass Fittings department at Lowes.com