well last week I bought one for my mother-in-law from Lulu hypermarket D-Ring road, there is a shop named Qasar-ul-Abaya on the 1st floor. they have lovely abayas and they do alteration as well, the range for formal fancy abayas was around 300 to 400 QAR, u can do the bargaining as well ( I did :) ) but this shop is good. try it u will also find simple abayas there.