If you want, you can make your own with a piece of plywood and some large soup cans. Empty out the cans, place in correct position and fasten securely to the plywood. I always practiced stacking with a mirror so you can see exactly where you are placing feet and make sure topline is correct. Sometimes just looking at them from the side isn't enough, a mirror works great to see what the judge is seeing.
Also, once you get ready to start lead training - make sure that you have someone tape you and the dog so you can see clearly what the gait looks like from the front, back, and side and you can make adjustments on speed and lead position if needed.
"Having heard all of this, you may choose to look the other way.....
but you can never say again that you did not know." William Wilberforce 1759-1833