I had a situation like that years ago.... 585 feet from the closest power source to the end of the driveway where I needed lights. At that point in time, I found a good alternative energy supply company and bought a 100 watt solar PV panel, charge controller and 2 six volt golf cart batteries. I built a system that worked, but for the weak output of the standard xenon or incandescent lamps I had available. Besides the fact that the draw was such that on cloudy days, we were lucky to get 4 hours of light.
Then came LED's . The first LED's that were made for landscape lighting ( supposedly)... Yucky color, weak output...etc.
Finally, the client said he'd pay for the wire run so I used a small trencher, dug the wire in and used a higher tap on my transformer. Lights looked so much better.
The irony now, I was ahead of my time. Had I built that system now, with 100 watt panel, and used todays' LED lamps, that system would have rocked.
Now, to help you with your question and to reiterate what James said.... to run that line and use a small transformer would be the way to go.
Furthermore, if you are a good salesperson and lighting designer, you should be able to justify to the client that since you are doing all this infrastructural work, that it'd be wise and more cost effective ( lower cost per fixture spread over the hard cost of the wiring) if he added some more fixtures. It's up to YOU to find places where some additional lighting would look good, be functional, serve purpose or create some focal points along the route.
Good Luck
George
