Take the old washer to just about any NAPA parts store. They should be able to match it up to a suitable replacement. There are only a few different styles and sizes, and they fit a wide range of vehicles, not just GM trucks.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!