Depends on how much you have already driven on the P Zeroes, this replacement can be expensive. In Karachi there are many places to do this but for a Yokohama, you can go to Sheikh Brothers on Sharae Faisal. Official importer and reasonable official pricing.
For Continental, Tire Point used to be a reasonable outlet but they are no more in Karachi, you can order their tires on the phone and have them delivered to Karachi. I just did it for a friend for Conti UC6 and got them fitted here.
Michelin is difficult, you will have to call up their official Distributor Zafar Enterprises and they would be able to guide you where to go.
All above names can easily be searched on Google and you can check each option.
Just asking, what issues do you face with the P Zeroes, too noisy, hard, uncomfortable?