Nokia’s highly-anticipated Lumia 900 Windows Phone smartphone is now available for pre-order from AT&T. The 4.3-inch, 4G LTE-equipped smartphone runs Windows Phone 7.5 and features a single-piece, polycarbonate design. AT&T is offering pre-orders for the Lumia 900 in either cyan or black for $99.99 with a new two-year contract. Those colors are expected to hit stores on April 8, while a glossy white version will be available on April 22. UPDATE 1:00 p.m. ET: We have received confirmation from AT&T that the online pre-order page is due to go live this afternoon, though a specific time was not provided. Ordering through AT&T’s customer service department or in a store may still be the best bet for now. UPDATE 3:49 p.m. ET: And it looks like the online pre-order site is now live. Order away.