microwave platter - 3 prong drive (Charlottesville near chs)

Hi I'm still looking for a microwave platter for my Emerson brand microwave. I think probably any "three prong drive" platter will do, not more than about 10.5 inches diameter. I've looked occasionally at Goodwill and Salvation Army, but to no avail. It's frustrating to know these get thrown out all the time, but I can't find one!