If he bought it online then he'll have bank statements or credit card statements. If he doesn't have the original copies he should be able to request copies from his bank. I've no idea about credit card companies as I don't use them. (Out of principle and out of laziness.)
I was also hoping that people would guess that you need proof of purchase in order to obtain a replacement. It is kind of obvious?
The point about making that comment was actually to highlight a rather unknown tid-bit of UK consumer law for those who were interested.
People generally assume that because it is outside of the standard 1 year guarantee period that there's nothing they can do. That couldn't be further from the truth.
To those who understand I extend my hand; To the doubtful I demand to take me as I am.