Holderread is of course cream of the crop, but they do not sell sexed babies. I have had good luck with McMurray--vigorous birds, good layers, nice birds. Not as perfect in stance or show qualities as my Holderread birds, but perfectly serviceable, and they have a nice selection.
I ordered some Metzer ducklings last year. I paid extra for sexing. While their feathering is not show quality by any stretch of the imagination, they are healthy ducks.
I have to agree that Metzer Farms is pretty good. I ordered through 2 different brokers and both shipments came through Metzer Farms. Plus Metzer sells Golden 300 Hybrids which are supposed to lay about 300 eggs a year. www.metzerfarms.com