The only monitor listed with that resolution (which is 5:4 aspect ratio, so it doesn't qualify as widescreen) at prad.de is the A.C.T. Kern FlatMedic IF2105A, but it's from 2000, so I'm not sure you can find it anymore. If you meant 2560x1600, you can get the Dell U3011 at various online stores. For 2560x1440, look for the Dell U2711.
It is a 10-bit grayscale medical grade monitor which is primary used for mammography and radiology. At $6,900 it is actually relatively inexpensive if this is the type of monitor you are looking for since variations of grays can mean the difference between normal tissues and cancerous tissues.