I dont have a cover on my 2910's pto shaft. The only ones I've seen on tractors are the kind that bolt or screw on. I suspect that manufacturers don't put the pop-off kinds on the mid-pto's, as they do on the rear pto's, is because they assume they would constantly be knocked and scraped off, especially when you are in brush. I have been belly up in gooey mud many times, both with the mmm on and off. A hose will easily wash the mud off, and you can add some grease now and then. It really hasnt been a problem.
I lift the mmm with the fel, but you could probably run a chain from the draw hitch over a fence or branch and down to the mower. Better hope that the rear of your tractor is heavier that the mmm before trying this, however.