Digital BW, The Print

A couple of you suggested painting the off white paper on the surface 
of the foam core - to white. An interesting idea, but we're talking 
about a
fine art print  which has to be of museum quality and both as archival 
and attractive as the papers we print on , One can't plan on either of 
those
for paint on paper, IMO.
  Also someone else  suggested Light Impressions as a source - 
unfortunately, they don't have it either.

Thank you all so far - please keep the suggestions coming:-)

Clay Price