You go to Lowes/Home Depot/ etc.
Pick up 4 blind nuts and bolts long enough for what you need, then grab some nylon spacers like the ones on this page.
http://www.lowes.com/SearchCatalogDi...true&Ntt=nylon

They come in different diameters and lengths so you just grab what you need. Bolts go through your X mount on the motor, then through the nylon spacers, and into the blind nuts.