There are many shops around Doha which sell non-original (Tejari) spare parts for cars. Have a look into these shops. There are several of them in Al Sinayia. If you visit any mechanic in Al Sinaiya they may get one for you if you agree to have the job done at his workshop. It will save you the headache of running around. Although, personally for an item like a wheel bearing, I would prefer to go for the genuine spare part but it looks in your case you do not have much of a choice.