You could tap in to the power for the dinette overhead light or the aft overhead light. Because of the ensolite insolation between the ceiling paneling and the roof we found it easier to tap into the dinette light.
Wire was run across the over-dinette storage from the dinette light, on the bottom close to the storage door opening. From there it goes along the port wall at the wall-ceiling interface. There is a removable trim panel near the dinette storage. Then fish tape was used to get the wire behind the paneling over the entry door and into the over-gaucho storage. From there it was run along the bottom back of the over-gaucho storage then to the desired locations for the lights. We just drilled through the bottom of the gaucho storage compartment to feed the wire to the fixtures, then screwed the fixtures to the compartment. Note that our fixtures were too deep to flush mount in the 1 1/2" or so gap between the bottom of the storage compartment and the paneling that faces the gaucho cushions. HandyBob, our wonder of an installer, very quickly made attractive wood shims to allow a professional looking install.
If you are going to run 12v back to the gaucho you may want to consider installing a 12v receptacle there as well. We find it quite handy. We have one just at the pass-through and another flush mounted against the closet. The wire for the closet receptacle came from the port side dinette base, where all of our electronics are, through the outside refrigerator
access panel, behind the galley, around the bathroom unit, and then into the closed from below. Sounds like a lot but only took HandyBob 15 or 20 minutes. I would take 2 or 3 hours.