There is a seat repair walla at Gizri. Near the 'Navy gate'. Can give exact directions if interested. Ive had first hand experience with him and he is good.
One more guy is somewhere near Tariq road. Do not know exact address but heard from people he does some great work especially at restoring old Toyota interiors.
I'm sure there must be somebody around the Plaza market but guess his work would be hurriedly done due to turnover of customers.
Hope this helps.