The Charles Darwin Research Station has a couple of gift shops that carry books, clothing, and souvenirs. Anything you buy there sends the profit back to the research station itself. This is what I bought there: These practical cargo pants (photo) are perfect for going on land visits to the various islands as they are 3/4 length with drawstring hems, so they won’t get wet as you sit in the panga or if you have a wet landing. They dry fast, too, so even if you get down on the dung-covered ground to compose a great shot of an iguana, you can just wash them out in the shower, and pronto! clean pants for tomorrow! They even have an applique badge with the Galapagos National Park symbol sewn on.
The big seller in the Galapagos is t-shirts. The ones at the Darwin Station tienda are nice, with tribal-style renderings of turtles and other animals of the islands.