I don't recall needing any lockpicks for the easter egg area.
Tingalf is a good source of lockpicks, if you have not had him arrested yet. Blake in Ars Magicana and Mpenzak in Verdistis sometimes have them.
Have you spoken to Finnigan in the Verdistis Ducal inn cellar yet? He gives you a quest to steal back his magic lockpicks from commander Kratus' desk/table. With the latest
patch installed they are unbreakable, and give you a +20 Agility bonus. Without the patch, they will break if you use the Lockpick skill with them in your inventory.