Hopefully either the helm or the belt drops for you soon!
(My main is a lock as well and I had that legendary helm too & it also took weeks and weeks of running both N and H to have the helm finally drop for me so I know your pain all too well.)
I’m a plate wearer and legs opened up a slot option. If you read the patch notes, their intent was to allow people set bonuses without certain pieces as long as they had the gems because the RNG is a fiasco with this expansion.