The player was not designed to take a specific fan. In fact, it wasn't really designed to take a fan at all.

Yes, there's a pair of pins marked "fan". Yes, the ventilation holes in the top are positioned so that you could mount a fan there if you wanted to. Those were put into the design "just in case", but were never used.

You're looking for some kind of specification as to exactly what fan to buy. There isn't such a specification. What you're looking for is any 40mm fan that's narrow enough to clear the drives and meets your personal noise requirements.