In a WotC source? there are none. There is the Guildmage of Waterdeep, which, since it is in the FR, is slightly easier to qualify for due to the education feat.
Your DM won't allow your sorcerer to take the Arcane Preparation feat so that your character can qualify for the Mage of the Arcane Order prestige class?
Wait for Player's Guide to Wizards, Bards and Sorcerers. Then get "Blessed of Mesos" Prestige Class and a Ring of Mesos from Relics and Rituals 2. Believe me, you'll be the envy of all sorcerers and wizards.