Thomas,
There are tons of sewing machines on ebay and at the local sewing machine
dealer and newspaper ads. Look in ebay for "Industrial Sewing Machines".
Sometimes you can find one at an upholstery shop where they have upgraded
and have the old one setting around. Usually the most you have to do is
replace the cog timing belt.

You want an industrial walking foot machine. There are a lot of 1930's and
newer Singer and Juki machines available from $100-500. They are "Bullet
Proof" and it looks like they will last for ever! Most in this price range
do not have a reverse bar, so you use the knee arm to lift the foot and move
the fabric backwards yourself.

They mount on a special table that has the motor and clutch assembly below
the table and a treadle to activate the clutch. They are not variable
speed, they are intended for the clutch to be in or out, not slipped.

I have two such machines and love them, one I equipped one with a newly
released DC Variable speed motor that is a direct replacement mounting wise
for the original motor, this makes going around corners a lot easier. The
motors are $350.00 and worth every cent of it.

If you are near Kansas City, MO, check with Missouri Sewing Machine Company
on Truman Road., they have some reconditioned and ready for use for around
$500.

Don Dando