Jaubertmoniker is lying to you. I have been to the Acme in question, and they do indeed sell rocket-powered skates. They are located inbetween the bakery and the deli counter.

Honest, I saw them just today. I was in the Acme to pick up some Old Spice High Endurance. Just after I tripped one of the stock boys and accidentally kicked him in the nuts when I went to help him up, I saw them. Really!