You just don't get it, do you? The issue is not necessarily that people do not trust you (some might, some might not), but that you are asking people to do something for you without offering anything in return for their troubles. Why would anybody want to do this!?
I'm failing to see where there would be trouble? so I give them a coupon code for headphones and they use that and pay me after it goes through. I figure there would be somebody out there who wouldn't find it to be such a big damn deal. If you guys needed a favor like this and I was looking for headphones, I'd say fuck it here you go man, and do it. Mountain out of a mole-hill.