Tyvek, like all polyethylene, is subject to UV degradation and discoloration.  I
n your application it will probably be stable, although I question how stable th
e inks might be.  Polyethylene does not accept adhesives or inks well.  As a
very convenient and perhaps relatively cheap source, check out Tyvek House Wrap
at your local lumber yard or building materials supplier.  It is used in buildin
gs to reduce air infiltration.  Although printed with logo, there is
plenty of clear area to work with.  The weight and surface should be OK for your
 purposes.  I comes in wide widths, probably 6 and/or 8 feet.