It is from my experience and also from AHL (email correspondence long time ago).
They claimed that they do not carry the replacement parts for cabin air filters because the cars assembled in Pakistan never were provisioned with it originally.
Sounds stupid - doesnt it, They just left two trays in there in which you drop the filters into. General Dumb455 reported for duty that day.
its not just in Pakistan, in the USA the 1997 camry has no cab filter, while some models of the lexus ES300 used the same HVAC box and had a cabin filter. You just need to drive to the lexus dealer to buy it, the toyota dealer does not have a part no. for it.