I crocheted several hats using the soft yarns for my mom when she was undergoing chemo for her lung cancer...I just googled crochet patterns for hats for cancer patients, and brought up a bunch of different patterns...most free...I am thinking you could do the same thing only for sewn patterns...here are a couple of links I found:
http://25thingsforcharity.blogspot.c...hemo-caps.html
http://thesewingjournal.blogspot.com...-hats-and.html
Sending warm thoughts and well wishes to your friends,
Kif
PS My mom is coming up on her 9th year of remission from lung cancer, she only has 1 lung, and is on oxygen full time, but she is a miracle!!!