The global Lumia 900 is pretty much the same handset as the AT&T version, with the notable exclusion of LTE. You still get a 4.3" ClearBlack AMOLED screen, 8MP camera with 720p video and 16GB of storage all encased in a polycarbonate unibody.
Anyway, the Nokia Lumia 900 is available for pre-order from Clove for £530 (€635, $845). The exact date of availability is still not clear (all Clove knows is it's going to be "some time Q2"). They are also not sure what color options they'll get, but will release the info as soon as they have it.