I know a lot of people use human hair for these and certain H20 masks but Martin Pèna on Facebook would know best since he has made his own H5 sculpt. Not sure if he has an account on here but I will reach out to him for you
Look for practice mannequin heads that beauty school students use, they usually have human hair and you can get them for relatively cheap compared to trying to get the hair in bulk on its’ own.