The part you need is 9N-7225; plate, as you stated but know that it was used on ALL 9N and 2N models with the 3-Speed Transmission. It can be found on any model year 1939-1947 9N/2N. The 8N Model was released in July, 1947 and now had a 4-Speed Transmission, the plate completely redesigned, and now was p/n 8N-7225 so be sure you get the correct part. It looks like a few options exist from other members. Just curious, why does the plate need replacing?
Tim *PloughNman* Daley(MI)