I spent a few days in Doha and searched for models but only found 1 place that sold pretty much what you can get onboard. It was a Qatar duty free shop inside the Oryx Rotana hotel near the Qatar head offices and the airport. All you will probably be able to get is the MegaWings 1/500 Qatar A330 and the B777-300. They sell 1/200 models too. They are pretty cheap around 12-13 GBP each after currency conversion.