I've seen some made out of what looks like aluminum tubing with hood pins welded in one end and a hole drilled in the other for the hairpins. Probably 16" to 20" long. Not factory for sure.
oh those things... i hate them... you better to just get the 2x2 foam and stick it to the bottom of the hood. then set it on the roof and forget about it, we have our race weight hoods up on top at mats with heavy winds and wont even flutter