I have some crayons that were meant for fabric. Bought mine a while back but here are some I found on Amazon.
https://www.amazon.com/Scribbles-306...39251182&psc=1
I also found these that say they’re best on 100% synthetic fabric. Maybe that’s why yours washed out.
https://www.schoolspecialty.com/fabr...SABEgI83fD_BwE