My favorite source for angel wing begonias is Glass House Works. They have a really nice, huge selection and their prices are pretty good. Some are marked down right now, too.
www.glasshouseworks.com Look in Tropical and House plants under B. The selection starts at the bottom of the first page and there are several pages of different cultivars.
(usually I agree all along with Ursula, but I must admit I've had a couple of really lousy, expensive plants from Logee's)