Sounds like you're looking for the last item on p 6 or first on p. 7 here:
I am removing a 4" cast iron drain and replacing with PVC. Looks pretty simple, small home with crawl space. Problem is finding a 4" PVC T with a 2" tap on side for bathtub,(to match the cast iron I'm removing). Because of limited crawl space, stacking 2 Ts may be a problem. The home has one central stack for all drains.
Thank you, That is it, now hopefully I can find it locally.
Maybe those at the link below can point you to someone who stocks it. But you can try calling real plumbing supply houses, now that you have what it's called. Shouldn't be too uncommon at supply houses for the trade.