I'v done this trick maybe it will work for you. Take 2 sided tape put on bottom of plate and stick to the thingy that turns. It worked for me
Years ago we used this place a couple times to fix our monster archaic Sears microwave (purchased in 1986). They did a good job and I see they are still in business. Might be worth a call to see if they can get the part. They are on S. Saunders St. right past the beltline interchange. http://microovensnc.com/