Is it the height that you are worried about? Do you have the high step? If so, you can use it at a lower height (I'd go no higher than 14", and 12" or even 10" are also effective (don't go any higher than having your knee at a 90-degree angle). YOu could also use your regular step platform and risers, turned lengthwise.
You could also effectively do step-ups using little or no weight. In the advanced high step training workout, there are sooo many step ups, done with exactly the same ROM, that I change them up. I do some with no added weight at 14". Some with 10# and 12". Some stepping off to the side.
I don't quite understand your question about using a "stepper" instead. Do you mean a "step platform"? To me, a "stepper" is a step machine.