You could take the spacer to your local hardware store and see if they have nylon spacers akin to the one you lost(at least you should be having 3 more spacers at your disposal to take dimensions off of. Conversely, you could contact Coolermaster and see if they can provide a kit for your mounting hardware in order to use your AIO. Lastly, you could look on Ebay and see if someone is parting ways with their mounting kit.