[pasqui]

i have a couple of iphones to sell of which i don't have an invoice of purchase. it is very difficult to sell an iphone at a decent price without a valid warranty. what is the best way to forge one?
i was thinking of modifying an amazon invoice , i know they can't verify it unless it is attached to their personal account. or i can get real invoices from private users on ebay, can i attach it to my iphone somehow making it look legitimate?
i welcome any advice from more experienced users in this area.
thanks