I think all the Kouji cels that have been seen
are in private galleries and not for sale.  I
beleive Heather from Usagi's House has some
in her private collection, and seen 3 others (1
from 1st OVA and 2 from TV) in other collections
and all were Not for Sale.  Would recommend
you just keep a sharp eye on FY cel updates on
dealers sites as there is always chance another
may show.