Here is the one you need but I don't have a clue where you might find it. It is a shaker/dump grate and was made by the Cowanesque valley Iron Works in Cowanesque, PA. It has No. 0 S.D. Gratering stamped right on it and the dump handle was made by the Indiana Fdry. Co. in Indiana, Pa and has No. 0 S.D. Drawcentergrate stamped on it.
I have good pics of both if you need them.
Your stove was made by the Gold Marc company right here in Monticello, NY and the model is "Monticello" Circa 1980.
I have one listed in the For Sale section right here.
Please keep us informed if you do locate a good replacement.