I know none of the stores sell it, and i dont want to go fighting random bandits until i find someone with EC, so I was wondering if there were any just laying around, like at a fighters guild branch or something

You can get an elven cuirass regardless of your level by doing this Fighter's Guild quest: http://www.uesp.net/wiki/Oblivion:Azani_Blackheart_(quest)

If you've a high-level character wanting it for the Master training quest, then you may have already done that one, and Rockmilk Cave would be an alternative, just for the number of bandits that might be wearing one. IIRC the archers are more likely to wear it than the blunt-wielders, who'd be in glass at high levels..