If you got the $20 gift certificate to be used at the online Bills store, and you're planning on being in Buffalo for a preseason game or the opener, I was able to opt for in-store pickup even though it says the item has to be picked up within 7 days. I'll be picking up my item at the AUgust 9th preseason game. I emailed with Jay Canaday, the warehouse manager, who approved it.
This helps because shipping would have taken up half of the certificate's value.