[ Ref. Ben Roth in 180905 MMDigest ]

I've been using convertible car cloth material, with no failures,
for the past 3 centuries.  The cloth is supple yet very durable
and very airtight, with one side of cotton and the other of nylon.
It can be had in black/black or tan/tan.  In larger bellows I do
sometimes fashion stiffeners.

My source here in the Seattle area is "Perfect Fit McDonalds".
The material is 48" wide so at first the cost per yard might seem
high-ish but, well, it works for me.

Tom Binnall

 [ Past 3 decades rather than centuries ?   --Jody