not too hard. You can get new Cannondales, Surleys, Fuji, Schwinn, Kona, etc fairly readily at most "real" bike shops (not chari shops). You might have to search a bit for the proper size, but you might get lucky. The new Fuji are pretty cool looking (FSA cranks and battleship grey)(crappy internet address logo on the top tube though). My local dude has the new Cannondale city models (Chicago already, Seattle and Boston on the way).

Depending on how long you will be here finding a used frame and parts and building up can be fast and pricier, or slow and cheaper. Yahoo Auctions just added more bureaucratic hoops but the prices are not bad at all. Lots of options.