A couple of summers ago we were in Costa Rica, and took a tour down the Tempisque River. To point out animals and such on the banks, rather than a flashlight or laser pointer, our guide used a small compact mirror to reflect the sun onto the spot where he wanted us to look. Cheap, easily obtained, no batteries, and no worries about getting wet - just the sort of low-tech solution that I love. I've since learned that this is a common trick used by soldiers as well.
BTW, our tour guides, Jose and Amy, were incredible. Highly recommended.
Less useful in the Cloud Forrest, I imagine ;->