Oh well, JPL has re-listed the Physical Parameter Table here: [link to ssd.jpl.nasa.gov]

That makes it not much larger than it was originally.
comet nuclear magnitude M2 20.6 mag
comet total magnitude M1 15.5 mag

That makes it somewhere around 0.5 to 0.333 km.

Oh well, it still should put on a very nice typical Sunglazer show as it gets vaporized by old Sol.