These help champs who auto, typically marksmen. 
These help anyone 
What about for a mage?
Old zekes boosted the AP of champs by like 10% for a small amount of time. But there is nothing like that anymore.
Maybe if mage supports weren’t already cancerous.
Abyssal helps a good amount, if you're able to get in range and stay in range for it. +15% damage is nothing to scoff at. Righteous Glory and Randiun AoE slows are also pretty nice to help your mages land their combo, but that's about as much supporting as they do. Other than that, the best thing you can do to help them out is peel for them. Keep them alive with locket and redemption, make sure to top them off with athene's whenever possible, and you didn't mention Mikael's in your post but the cleanse on that is amazing for keeping immobile mages safe from stray CC. Not to mention the +20% healing and shielding power you get.
Nah thanks mages are already cáncer dont make it worse
I guess stuff like
Twin Shadows 
Plus if you're a mage support just build AP. Simple as that
no thank you.. If i see one more brand or lux support im gonna tear my eyes out
Well if the experimental Karma changes go through her W will reduce ally cooldowns which helps mages more than most ADs, and Zilean's passive xp boost is more useful for carries that scale heavily with levels like mages, so there's some support catered more towards mages even if it's not in item form.
Lulu used to give AP and AS. Then they removed the AP since it had too much synergy with ADCs who scale with both AS and AP.
