I know it's several months later, but....
Haunt your local Craigslist listings - sometimes walking foot industrials pop up for something that's actually reasonable.
If you need just a straight stitch (upholstery, drapes, many non-stretch wearables, that sort of thing) then you'll be able to find a used straight stitch walking foot industrial without too much trouble.
If you strike out with Craigslist, check with your local "old sewing machine guy" shop - pretty much a shop that just repairs sewing machines, not a "vacumn and sewing" place - they will likely have an idea of who might have a machine of that type for sale, or be able to find one for sale.