Try an Ancona, Andalusian, Appenzeller Spitzhauben (mines halarious!), Dorking, Hamburg, Lakenvelder, Sicilian Buttercup. I have all but the Buttercup, which I'd like to get. Nice white eggs.
I have the buttercups (they are from sicily like my grandparents so had to get a couple), they lay medium white eggs, but aren't real friendly birds. I probably wouldn't have them again. If I were getting a white egg layer, I would check into the delawares---a great dual purpose breed that lays big white eggs too.
your question on what hatchery to get white leghorns from. i just ordered 25 white leghorn chicks from meyer hatchery . they will be arriving week of march 7th. i checked out a few hatcherys on pricing and meyer seemed to be the better deal. that and they were the closest hatchery to me that had the pearl leghorns i wanted.