Problem - If mages wish to itemize in order to obtain 40% cooldown reduction, the only ways to do it without a use of 2 item slots is 9/0/21 (which they should use anyways XD), CDR blues, and either Blue Buff, Nashors Tooth, or Frozen Heart, which both have lackluster stats for most mages ***(Nashors Tooth has Attack Speed which most mages will never be using, and Frozen Heart only gives armor and mana, and mana is the "worst" stat to have late-game, especially since most mages will get Banshees Veil and Archangels, solving any and all mana issues.)***, or to use something like Deathfire Grasp and Blue Buff, however not all mages require something like Deathfire, so sometimes that too can be a lackluster choice. My suggestion will attempt to bridge the gap between AP cooldown reduction items, and Support cooldown reduction items.
Item with a cool name (i'm bad at names, my apologies, and I hope this doesn't negate my suggestion)
Component Parts -
Fiendish Codex - 1245
Soul Shroud - 2105
Recipe - 650
Total Price - 4000
+600 health (A small upgrade from Soul Shroud, which is what this item will be focused on, small upgrades to the components that add up to a fairly powerful new item.
+50 AP (This is possibly the largest upgrade in the entire item)
+10% Cooldown Reduction (Because 25% AOE CDR is WAYYYYY overpowered in my eyes)
Unique Aura: +20 Mana Regen/5 Seconds (just combines the two and adds an additional 1 because 19 is such a terribly odd number)
+15% Cooldown Reduction
This is my item, in my eyes it is a good item on heroes such as Zilean or Janna who benefit from Cooldown Reduction more than anything, but AP helps them out.
This is also a good item in that Fiendish Codex is a fairly good early game item, providing mana regen, as well as Mana Manipulator -> Soul Shroud rushing is good for the bonus health on those heroes who love cooldown reduction.