Why would you want to shoehorn a different gearbox in???
Yes anything in Pakistan is possible but in general this kind of attitude has contributed a lot towards the screwed up state of affairs we see all around us.
First off there is this urban legend, a myth spread by our sooper dooper mechanic bhais that Auto gears are faulty, impractical, irrepairable and what not. So if youve been told such fairy tales please dont believe them. Your original 'box may very well be useable.
If you still want to go for a manual 'box, I strongly suggest you go for an original Vitz unit. It might very well be a bolt on fit.
Best of luck.