Py,
It depends on the make and model because the market is somewhat limited, and most places don't carry parts for anything outside the HP, Dell, Toshiba, Acer models that are the bulk of the laptops available here. Cecomsa on Romulo Betancourt between Churchill and Nunez may have what you're looking for. If they do, they'll fit it for you, but perhaps not while you wait.
If it's anything more "exotic" than that, your best bet would be to buy on line and have it Fedexed to you here. As explained in the other thread, on most laptops it's fairly simple to pop out the keyboard and replace it as long as you use logic and not brute force.
Bryan