Mike,
Are you referring to the in dash nav unit? The kind available in the UK and USA? TV is not available on that model as far as I know. Hmm... There are two newer versions of 'official' Mini navigation units that do have TV standard...They are both made by Panasonic and have film antennae. They might have a part number for it...
Anyways, drop Mini Japan a line at this address:
info@mini.jp
They have somebody that speaks English and I think they can help you...