I have an old sprayer from Glacier Bay, (at least 20 yrs old) and I have broken the lever at the back of the sprayer. I am hoping that someone could direct me as to any possible supplier of old product.

Most sprayer units are replaced with a universal type. Unscrew the 2 parts. If you are lucky, the top replacement will screw onto the old bottom. If not, remove the small c clip that holds the bottom on, install a new bottom and c clip and screw them back together. HD, Lowe's and others sell universal replacement sprayers.