Re the recent posting mentioning "Polylon" for pouches.  About 1971 I
rebuilt an upright Ampico using Polylon for the pneumatics.  Now it is
beginning to fail with the plastic coating coming loose from the nylon
fabric.  I purchased it from Nelson Barden (of Barden and Clark) in
Boston.  It is easily attached using PVC-E.

Perhaps a newer version of this material is different from what I have,
however, I question it's suitability for pouches, unless they are large
enough that flexibility doesn't matter as much as it would with small
ones.  If it does not have pinholes, it is airtight.

Pat DeWitt