Another option, since you ask for some homebrew alternatives, is a variation on the Archivist class... the Biosoph which you can get to from my signature below. It is essentially an Achivist (from Heroes of Horror book, or freely available from the WotC website), but with its focus changed from Occult, Fiends, Undead and the like, to Nature, Animals, Plants, Fey, Elementals, and other related critters.
The overall effect is a scholarly class with a focus on nature, maybe a bit more apprapo than a shape changing style of druid.
I would also point to a relatively recent dragon magazine that had a class called the Sidhe Scholar - sort of a Fey Magic Student., but not necessarily built specifically for the city.
Like Sound of Azure said, the standard Urban Druid is neat in its own ways, but still seems a bit out of place in the city to me.
(waves to SoA - College A&PI is killing my gaming frame of mind - even had to drop out of my Sunday regular game. No game design going on here lately. Hope all is well with you)