About 10 years ago I was involved with a group making dignity gowns for women undergoing radiation for breast cancer. At the time in our area women undergoing radiation had to lay on the table fully exposed, an acquaintance started making the gowns after her doctor friend told her how demeaning it was so she designed a gown where only the area being radiated had to be exposed.
We used our own fabrics, often sending out appeals for fabric to different sewing groups. Did receive much response, most of it usable. As anyone knows who has received donated fabric sometimes it is just too moldy or bug infested to use, but was donated with good intention by families clearing out grandma's attic or garage.
Through an Internet search I found a list of American companies producing cotton fabrics, there weren't many, but I wrote to them about our mission, I think I included the form for charity deduction, can't remember all the details. One company did graciously respond and sent several bolts of beautiful cotton, perfect for the gowns.
The group eventually disbanded, the local hospitals started having more rules about outside donations due to infection risk but the gowns were well received at the time. Many of the women receiving them sent beautiful notes of thanks.
So it is worthwhile to try.