One piece of aluminum 1" x 1/4" x 30".
Cut one 6" piece off to use for second fork.
Drill three holes.
Three 5/16" bolts, two of them with smooth shank and threads.
Cut heads off smooth shank bolts and dress with file.
Smooth shank bolts can be adjusted in or out to make up for difference in thickness of the two pieces.
Cost $12-$14 US
Easy to build but takes a little time.
Have seen some on the net made with 1/8" aluminum. IMHO 1/8 is not sturdy enough. I recommend 1/4" thick aluminum.