AAV and bathroom sink

[adiner]

So, floor replaced, faucet installed and ready to hook up and put in a new trap. Was an s trap and not sure whether to replace with new s trap or put in a p-trap and AAV (plumbers say the former is ok, but others say that code requires at least the p trap, if not also with AAV). The problem that I have is that the pipe running into the floor is 1.25" and pretty much every AAV I have looked into (studor, oatey are the main brands that come up, I think there was another one too) are 1.5" at the smallest. I read through the product listing for studor and I'm also not sure if the mini-vent is for 1.25" or 1.5" pipes as it seems to suggest the latter. As this is a bathroom sink with a 1.25" drain, it would seem that I should keep it continuous with 1.25" throughout. I've seen that there are various couplers with a 1.25" and 1.5" end, so I don't know if it would be fine if I use a 1.25" sanitary tee, another piece of 1.25" pvc and then connect that with a coupler for the 1.5" AAV. Also, that would be a lot to connect given that there's not a lot of space underneath. Unless I've overlooked any products out there that would fit with 1.25" piping, I'm not quite sure what to do at this point. Any suggestions would be greatly appreciated.