Anna:
first think about your height and whether 14 inch step is what you need to perform the same function or whether it's more like 15 or 16 since you are also 5 ft 8 like me, right?
I either use some wooden blocks I had kicking around my basement and place those on top of my 8 inch step, or I just use a chair from our dining table that is totally unrefined with plastic top, not fabric so I do not mind trashing it, anyway the kids ripped it when they were young, so who cares anyway. This is around 15 inches I believe, or maybe 16 inches. Cathe's mini-topper height may not work for all of us at different heights. As long as you have that 90 degree angle with the knee when your leg is on top of whatever contraption you find to work for you that is solid and stable, then you go girl!!!
Clare