You can check your thrift stores and churches.
You know, Goodwill, Salvation Army, and many churches also offer a clothing pantry. Some senior centers do, too.
You might also post a link on Freecycle.com. Describing what you need. Many members there are happy to destash to a good home.
Another idea? Take up painting and make your own textiles. If you learn to stencil...it is easy peasy. And muslin is cheap. There are pre-cut stencils you can buy...or just make your own. Don't limit your shop to the craft stores. Hardware stores often have neat stencils in their paint/wallpaper section. For using on wall borders, and such. But they could be used on fabric.
Stenciling is easy. Get a good pounce brush, and some quality fabric paints. And you are ready to rock and roll.
Fabric Sizing...the important key so that the ink/paint on the fabric does not "bleed" under the stencil. StayFlo Liquid Starch is my go-to. You get that where you buy laundry products. Instructions on the label. Pre-treat the fabric with it so it is stiff.
There are also temporary spray adhesives to help you on the underside of the stencil...to keep it in place while you work. Think Post It Notes
Hope this is helpful.
COOL! thanks for the input! I am a huge thrift-junkie so I have been checking there when I go, but it didn't occur to me to think of freecycle or CL. durrr