However if you are after several hundred individual bags,
then you could use air-drying clay and your own mould
(using the commercial stuff as a size guide to stamp 'em out in quantity).
For this type of stuff your mould needn't be too fancy.
Just 2 pieces of close grained wood with a 1/2 bag size cavity in each.
Two trackpins or small nails should be sufficient to ensure alignment as the halves come together.
If you line the cavity with a teabag settled in with a thin smear of white glue,
then you might be able to stamp a fabric texture into each bag when it is moulded.
Provided that the bag comes out of the mould cavity OK,
you should be able to make a bag in under a minute.
Something like talc or baby powder rubbed into the mould cavity and separation plane,
might help the clay release from the mould.
If you slightly overfill the cavity,
then this will give you a side seam that can be trimmed after the clay hardens up.
With a bit of practice you'll be able to estimate pretty accurately,
how much clay you need for each bag in the mould.
Also remember any "not-so-successful" bags,
can be buried in amongst a pile of good bags,
Good luck, and let us know how you go.
Unanderra in oz