Great website is www.Chemocaps - quite a few choices ofpatterns on offer.
There's also a website called:hatswithhair.com - (Tampa, FL) they're a very friendly and helpful company. The hair is attached to a hat for a 'natural' look of hair peeking out from underneath. The hats are said to be more comfortable than a full wig.
Hope this helps.
All the best to you and your friend