I just go to the local fabric store and buy a yard or two of clear vinyl they sell for seat covering for about $6. Cut it rectangular and large enough to go down the sides, slit the corners out, and use some vinyl glue to seal the corners and flip it inside out so the corner seam is inside. They will actually hold water pretty well and I can add a small soap dish with a lid and some soaked water-holding gel beads for plants in the dish to keep the humidity up while they are covered to help with the nozzle clogs. Plus I can see through it and turn the printers on-off so they can do a bit of pre-cleaning and pumping up even though I might not need to uncover them.
I live in a desert climate and the things will plug in a couple of days if not covered with the vinyl. For longer storage under the vinyl I'll fill the capping stations with head cleaner, enough to wash out the color in the pads. So far so good.
SG