Empathy will indeed identifty the lead guy, but you still can't Mind Trick the lot of them into thinking you have money when you do not.
It would have been SO easy to do a Qui-Gon mind trick to make them think a dodgy substitute was fine- at least long enough to unlock the generator- but that, as I say, would have required prep.
Iron Will maintained, Empathy to see who is in charge.
"Show me the generator. I've been through some rough experiences; the last generator I tried to get, I ended up losing not only my companions and my money, but also my nervous system..." Rand shows them the wires at the back of his neck. "...and my heart." He raps on his chestplate. "It was more pain than I've ever gone through in my life, and it turned out that there wasn't even a shield generator to begin with. I have no reason to suspect that you wouldn't do the same; you outnumber us, you have our ship, you could easily walk away with a profit without giving us anything. I assure you, if we see the generator, the money is yours."
(crosses fingers)