Hey Veronica. I just love step aerobics. I took classes in college an for a couple of years afterwards. I use to try to find videos to use at home but I had no luck. To me they all had similar moves and I became bored quickly.
I'm not sure if you are asking specifically about step aerobics exercise videos or other exercises you can do on a stepper so I will answer both.
Regarding step aerobics videos there is a woman on Youtube by the name of Jenny Ford that has a series of hour long step aerobics videos that looks promising. The videos are high quality, the video camera stays stationary and her instructions are clear.
Also there are some exercises you can do on a stepper such as tricep dips, lateral shuffles (where one foot is on the stepper and the other is on the floor and you alternate really fast) or when you "step step" on the the stepper and "step step" on the outside of the stepper really fast.
I'm not sure if you strength-train, but you could also lay on top of the stepper and with your feet on the floor you could do bench presses, tricep overhead extension (lying down) or chest flies.
Thanks for your post by the way. You gave me inspiration to dust off my stepper and give a video a try some time this week. It's been a long time so I know I'm going to be rusty!