I do not have one, but agree that they look amazing. Appear to be extremely well built and like the modern look.
According to this
Link they do not come with a top because, as they put it, "Maximum Oxygenation and to Allow Plants to Rise Above the Water Line".
A couple ideas would be to make one out of lexan, or have a plate glass company cut one for you.
"If you've heard this story before, don't stop me, because I'd like to hear it again." ~Groucho Marx~