is there a list of these items anywhere?

I know of a few, such as some specialty amulets, the diadem of the savant, and I think the officer's bracers and boots?

I don't think that there is anything with an armor rating that isn't considered 'armor'.
Officer's clothing (so I've been led to believe) is technically an armor. You'll just have to stack potions and enchantments to get a good rating for a mage.

You'd have to get clothes or robes that you like and enchant them enable to use Mage Armor, but other than that I don't think there's clothing with an armor rating like normal armors.