It seems that some of the legendary quality armours sold my vendors do not make complete sets? Specifically here I'm talking about devastators chest and right grieve, where as far as I can tell there are no items that have the same look? It seems to be metal armour with a white overlay. I've seen atleast 70 legendary armour pieces as drop by now and not found one with the same theme. I'm just wondering if anyone can confirm this?

You buy all the pieces off of multiple different vendors

It's a propane tank(s)...look at the neck parts, they're gas grill tanks.