Question Lock Nut for crossbar/H-adapter size

[SoCalDiver07]

Can anyone help me. I picked up a set of LP72 twins and the crossbar/H-adapter is missing the locking nut. I dont have a way to check the thread pitch or size to order a couple of nuts. Can anyone point me in the right direction by either supplying the nut size and thread pitch (preferably) or link to order a new set without paying $16 in shipping? I am assuming its a standardized part. Here is a pic to the part I mean. Thank you for any help.

 

[inquis]

Are you sure you need it? I leave mine loose to allow the manifold to rotate if it ever nose dives off the bench.