I note that the OP says "A client lost his and I need one to fix his iMac." In other words, this is not just casual copyright infringement but something that is being done for profit (I assume that he charges his client for work done). I don't know about the US, but in the UK that would constitute a criminal offence.
I wouldn't let someone like that within a hundred miles of my PC or Mac. If I pay for a repair job to be done I expect it to be done with legit materials, not knock-offs.
And all for the sake of saving $25.