the problem with energy champs, (and resourceless champs) is they're supposed to have lower base damages, and or longer CD's so they cant spam indefinitely or as strong as people with mana.
as when a person with mana does it they eventually can no longer do it. so their stuff is supposed to be a big stronger or more useful.
its a shame riot doesn't get that.
now as for items which are directly related to energy users, there just aren't enough of them to really have their own items, and they can make due with lots of already existing items, so i dont really see a purpose to give them their own unique items which the majority of other champions cant benefit at all from.
(only 6)