I may have a solution for you, but we don't carry that specific Thetford part you're looking for. However, a toilet flange is a fairly universal part and we have two Toilet Floor Flanges available depending whether you need a male or female flange.
You could use the Valterra # T05-0782, which is a 3" male threaded flange or the Valterra # T05-0784 which is a 3" female threaded flange. You will also need to use the Valterra RV Toilet Floor Gasket with Hold Down Bolts # Q23653VP. view full answer...