As an alternative to Theron’s product recommendation (I am not familiar with either of those products), you could also try a kit for restoring clear plastic headlights, like this:
https://www.amazon.com/Mothers...enewal/dp/B00GZLMEPM
The washer bag is probably color-impregnated vinyl and it doesn’t look like it has anything silk-screened on it, so if you’re dealing with an aged stain, maybe the very mild abrasive in the Mother’s kit is just enough to remove the stain without petrifying the remaining vinyl beneath.
DO NOT use a petroleum product on vinyl. That will affect the vinyl and it becomes hard and brittle.