While I'm a big believer in buying "marine" products when they are actually proven to be Marine grade, I am less certain about other products especially ones that will live below-decks. These items came directly from IKEA.
The top photos are of the LEDBERG LED 3-piece light strip for $14.99 (30in long). By simply cutting off the 120v to 12v transformer you get a 12v system. It has a nice simple clip system.
This is the JANSJÖ LED USB lamp for a very "non-marine" price of $4.99. I plan to have a number of 12v sockets at various places around the boat and if you need a light you plug in one of these.