‘Iron on embroidery stabilizer’

Or something similar to that wording.

Rub it a bit on something like cement ground or a nail file.

maybe this isn't feasible but what about adding a lining around the inside of the waistband? if you don't want to sew or adhere it you could use bobby pins to hold it in place

Vinegar's a good shout. You might also have some luck soaking in fabric softener.