I will be ceiling mounting my new AX200. Is there anything that I can use to cover the lens instead of using the cap. Clear filter? Hood? I want to protect the lens, but I do not want to have to get to the ceiling to remove the cap each time.

As long as children and pets are not able to get to the lens you should be fine without any cover.

To add to Reconlabtech, you want to avoid cleaning the lens unless someone touches it. You'll see some dust/debris on it, but it shouldn't affect the quality of the projected image.