Favorite fabric store
You can also check at Joann.com
not sure, however you can buy florescent off white fabric that can do the same thing.
They sell white cotton fabric which reacts to black lights naturally by glowing blue, if that's what your asking. Otherwise they also sell glow in the dark fabric paint in spray on, brush on and squeeze on types. These would absorb light and glow in the dark or react with a black light.
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