This is a 5-minute video by a couple of physical therapists who have a Youtube channel I subscribe to:
This is a 7-minute video by an orthopedic surgeon:
Doctor Jo has a finger strengthening exercise that uses a rubber band:
I also have hand weights (1, 3, 5, and 8 pd weights), a set of those little squeeze-y balls, and a hand grip I use.
I do exercises aimed at strengthening my hands, wrists, and forearms 3 times a week.