I was in the same boat a few years ago. You may be able to get a few samples from his doctor's office. (whoever originally prescribed it.) Also, I bought it from Mexico by mail. It was a few years ago, but I think if I had paid cash at the pharmacy it was about $200 or $300 dollars versus $50-$75. It came in the exact same purple plastic dispenser with a sealed wrapper inside the box. Good Luck to you.
Here are two websites that you might try. The second is by GlaxoSmithKline, the maker, of Advair.
http://www.patientassistance.com/B128-advairdiskus.html
http://www.rxassist.org/pap-info/company_detail.cfm?CmpId=125
I hope this helps,
achilles2