If you’re looking for a little stocking-stuffer for a paddler, get a whistle. Canoes, kayaks, and stand-up paddleboards are all considered to be vessels, and as such, they are required to have some sort of “sound signal” device on board. For paddlers, a whistle is the easiest way to meet that requirement. You’ll want to get a “pea-less” whistle – not the kind of whistle used by referees. If you get water in a referee whistle, it stops working. Prices are typically $5-10 for many of the whistles favored by paddlers. Low-profile/small size is appreciated since most paddlers attach their whistle to their life jackets.
You should be able to find whistles like the “Fox 40” at better outdoor stores and marine stores, but if you can’t find something locally, I have several choices shown on my Amazon.com Local Associates page.