Well, I've got a wing with a backplate pocket that holds my DSMB securely out of the way, ( a small rubber chicken hangs from the DSMB strap, hence my internet name). Tusa knife on the LP hose, Torch sits through a 45 deg D ring on my weightbelt,( for clipping to a line before removing when climbing back into a RIB), and everything else goes into a pocket.
Mind you, i don't dive with a metal detector,(yet). How big is it ?, Couldn't you put some sort of clip arrangment on your cylinder bands, like the ones some people use for flags ?


Alternatively, Jump into water then craftily clip it all to your buddy.