Venus is about as close to "earth-sized" as you are ever going to find. It is in just the right orbit too.
If we are ever able to spot "earth-sized" exoplanets, the real trick is going to be distinguishing the Venus-like planets from the Earth-like planets.
That would be a few years off yet; probably a decade or so before we start getting spectra from earth sized exoplanets. Once that data is available we'll know which it is.