I am a big fan of custom made covers for all studio equipment. Dust kills the quality of connectors, sliders and switches. If possible I try to use the dust covers from the instrument or equipment manufacturer. Otherwise I try to look for a Decksaver, because actually these are very clever desk space savers as well. And they fit like a glove. All too often however I find that there is no custom cover that exactly fits.
I tried to find custom covers for the Yamaha 01v and the MicroKorg, but couldn’t find any. My current solution for this is to buy flexible transparent foil and have it cut to a little more than the surface area of the device. It can attract dust, but at least the dust does not get in the equipment. It also looks quite professional and is easy to pull over the surface and slip away again.
For me this beats ill fitting cloth covers and other half baked solutions, like putting it in a box. The best alternative could be to buy thick sheets of perspex and glue a custom cover. There are shops that support you in building your own perspex cover. It will however never be as sophisticated as Decksaver covers, with extra space for knobs and bends in the device. If you’re on a budget, at least put a sheet of transparent foil over your equipment and make it last longer.