I made a quick cover for my machine out of a 2 yard practice I had finished. I simply folded over the raw edges for neatness. Then I folded one end in thirds and sewed the middle together for an inch or two. This created two corner "pockets" to put over the handles on one end of the machine with the rest to cover to the end of the machine. It could be a little longer but this works for me.
I park the machine at one end of the table and cover the table with two old sheets. I only started covering the table recently as we moved and the longarm is now in an unfinished basement(more chance of dust from the ceiling).