Used to do the same. Thankfully there are glass splatter guards out there, some of them with plastic handles on the outside. More expensive than you would hope though, I suppose because it's such a niche use, but it's not as if you're going to be buying many glass microwave covers in one's lifetime!

I put a paper towel on food in the microwave to stop splatter. As a bonus, I've found a moist paper towel helps when microwaving leftovers that got dehydrated in the fridge.

I usually put a saucer or plate over the top!