How can I find vacuum filter fabric?

Hi Kay. I've never tried it, but here's an article that recommends cheesecloth as a DIY. Perhaps it will help. https://www.doityourself.com/stry/make-your-own-vacuum-filter

I saw that at a fabric store once

You might think about using a piece of pantyhose fabric.

You might try an upholstery fabric place or a place that sells auto upholstery materials and supplies.

Do you have a picture of the old one, it will help so we can better advise you.

If you know the name of product. You can google the company. They maybe able to help. See if you can find model number, add it in your search.