This mod (my first) provides unenchanted copies of all the mage robes and hoods.

It can be bought from Radiant Raiment in Solitude. Not all of the robes and hoods are available at the same time. If the specific robe you're looking for isn't available, wait for the inventory to restock. It usually takes about 48 to 72 in-game hours to restock.

Source: http://www.nexusmods.com/skyrim/mods/53633