There is no reason that modern air tight cloth could not be made.
The problem is the limited market for it.  Players have an unusual
combination of requirements so something commonly available probably
will not do.  But that does not mean that something equal to or superior
to the old stuff could not be made.  This was common low cost material,
not the best fabric nor the best coating compared to what is available
today.

To summarize the needs: the cloth needs to be very thin and flexible,
and able to take sharp bends and not fail over a long time.  The coating
should not peel or work harden, and it must be glueable with some sort
of long lasting and strong adhesive.  This should not be a problem, but
people need to get over their insistence on originality.  Besides, the
original material was not that great to begin with -- it was just chosen
to be the cheapest stuff that would work for a while.

A while ago I contacted a company that makes coated cloth and they
assured me that they could make something suitable but that a very large
minimum order was necessary.  I did not want to invest thousands of
dollars in thousands of yards of stuff that no one would buy because it
was not like the old crap.  If there is enough of a market it could be
made but everyone disagrees about what they would use so it is probably
a doomed project.

Another possibility is to make your own.  Bed sheets are available
today made with long staple Egyptian cotton in thread counts much
greater and of much better consistency than the stuff used for the
old cloth.  It is not rocket surgery to coat cloth with a sealant.
The problems are finding the best sealant and developing techniques for
applying a uniform coating that penetrates the fabric and insures air
tightness.

Actually, air tightness is not as critical as stability.  I have a bolt
of urethane coated nylon that was tested by someone on this list.  He
found it to be leaky but the total leakage was not enough to affect
performance.  If the leakage stayed consistent over time this would not
be a problem.  It might also be possible to apply an additional material
to seal the tiny pores in the urethane coating.  I had three bolts of
this stuff but I threw away two bolts because no one seemed to want it.

I think that synthetic cloth will last longer than cotton unless just
the right cotton is specified, and who knows how to do that other than
the long dead player engineers?

Spencer Chase