I assume the big plastic connector next to the SATA is supposed to power a hard drive. Indeed I have a bunch of cables lying around that have 4-pin molex on one side, and the SATA power connector on the other.
But: all my cables are male on the molex side, and the Espressobin board is male, too!
Opening a random PC next to me reveals that its power supply provides female molex connectors, so my adapter indeed fits. Unlike the Espressobin.
@TheLinuxBug: I had been trying to be really clear in my post, but apparently I failed.
I have plenty of the connectors you point out, the trouble is, none of them work, as the board is male and the disk is male, too. That seems to be a mistake on the board, the Moles should be female — or even better, be a SATA power connector, not Molex.