Have you looked at phone apps? There are a number of them available. I'm sure at least some of them are free. They may not be as good as a dedicated shot timer unit, like PACT, but for your purposes they may be enough, at least to start out without spending a lot of money on a timer right away. I used one of the free ones, can't remember which one, but I only used it when practicing dry fire drills. It worked pretty well. If I can figure out which one I used, I'll update this post.