Yup, from the store where you get an outfit you can ask the person who works there to get that shalwar kameez to be in your size, and most of the time they will do that and this will obvioulsy cost you some money as well and it might take about 2 to 3 days for them to get your outfit back to you.
And if you have time issues just go to the nearest tailor, Lahore has really good ones, especially in the Gulberg area.
Karachi is the best place for shopping for Pakistani Clothing, even better than Lahore. Park Towers is a good place to get started although its costly and Zamzama is good for bridals, they have a lot of variety here.
Stay in the Clifton area for the best quality and trendy clothing.
There are some good tailors in Clifton, especially in Uzma Center, if that place still exists
I know of their boutique in Defence, Lahore! The workers there are nice and they do the excellent alterations in less than a week for 4 dresses or thats how good they were back in 2004-2005.
Fortress shop ppl didn’t do the alteration for me as desired so I just bought a few outfits and got it done from the tailor.
Liberty is a good place to shop for clothes and Stylo in Liberty is good for shoes!