toilet vent

Hello, just purchased a home and toilet on first floor sometimes has a strong sewer smell. Replaced wax seal, original looked good. Still smells in bowl, not near base of toilet… - From the looks of it I just need to add a 2” vent to this before the main (goes right to second story toilet? -...

Howdy, I've come upon a missing link. I'm remodeling a bathroom, and the toilet vent is 2.5" ABS. Did companies stop making these fittings? Just too odd of a size? I'm only replacing the pipe through floor and hooking back up to old "Y", don't want to have to run new 2" all the way through roof.