I think the D200 will write to a card at about 10MB/s. Even given that cards are generally given exaggerated ratings, most 20MB/s (133x) or 30MB/s (200x) will be more than fast enough for the D200. Buying anything faster will let you offload to your computer faster using a card reader, but not help at all in camera.
Try
MyMemory or
7dayshop.
I think it's worth sticking to the major brands - Lexar, Sandisk, Kingston.
Chris