Urinal smell in 2008 Prius - possibly from A/C ?

Does anyone else have a urinal smell coming from their A/C ?
I recently took over my parents 2008 Prius.
I remember around 11 years ago the day they bought it used.
It had a sweet, putrid 'urinal' scent pack smell to it.
I thought the used car guys had placed a scent pack in the car, but I can't find it.
11 years later, and the smell is just as strong as day 1, despite trying all sorts of odor absorbers.

I thought maybe a cat had got into the car, but the smell would have gone away after 11 years.
I can't trace the origin of the smell, but I notice that it seems possibly stronger with the A/C on, but this may be the wind blowing the smell into my face from elsewhere.
My next thought was the cabin air filter, but no. The smell would have gone away in that too after 11 years.

Any ideas ?

 

Thanks !
I figured this might be the issue, but would the smell be just as potent after 11 years ?
This is my first full day with the car, so I'll have a look at the filter maybe this evening.
Edit : I'll look in the manual and online to find the filter location, but is there more than one, and if so which one did you change ?
Do you just clean the things, or do you have to buy a replacement?
- Thanks