If it doesn't say 100% cotton on the package then it probably isn't
Most of the gauze/pads I've found are Rayon Polyester blends
I've looked at CVS, Walgreens and RiteAid
CVS and Walgreens have the 100% cotton "Sterile Bandage Roll", 4 yards for about $5
RiteAid is the best, they sell the 100% cotton gauze pads individually, about 5 for $1
I've found that the right stuff always has "100% cotton" on the package