In World of Warcraft can you buy a reputation for stormwind

Yes, reputation for any of the base Capital city factions can be bought. There is a cloth quartermaster in each capital city, where you can hand in 60 units of cloth of a certain type until Exalted.

First you can hand in Wool, then Silk, then Mageweave. The final quest is to hand in 60 Runecloth, which is also the quest which can be repeated until you are Exalted.