Darnassus Tabard

Unsure on where i can get the Darnassus tabard to get the saber mounts from getting them to exalted

There is no such tabard in wotlk. You have to do quests for the night elves

Actually there is one such tabard. From the Crusade grounds in Icecrown when you become a Darnassian champion.

Thou that tabard is not in any way related to getting reputation. You either quest for that or you quest.

Also you can get to exalted by just becoming a city champion in the argent grounds.