99% xli have power windows installed in them.means it is possible infact its a bolt on fitting.you have got basically two options in the market regarding power windows
1- Buy the chinesse motors along with the buttons and get them installed.This method is actually a cost reduction method and you wont be haivng much problem in finding the chineese stuff.This installation will cost you like 8k.
2-Go to bilal gunj (in case you line in lahore) and get the original motors and switch with the original door panels.This method would be a neat one but will cost you more.3 years back i got my xli converted to gli from Amjad motor with original motors and buttons plus motorized side mirror, central locking,security system at a cost of 22k.
Rest its your choice.