Do they make caps for a sump pit?

I don't think so, all I have seen are flat. Installing a submergible sump pump would make a flat cover work. I installed a plywood one, with an "in-line" exhaust fan sucking air from it and blowing it outside as we get a sulphur (rotten egg) odor when it rains a lot. This method also creates a negative pressure under the floor slab which would help to remove any radon gasses. It is installed with a simple timer to run 1/2 hour twice a day. If the smells come back during the rainy season I increase the time of the fan running.

I'll bet there is more than one person out there who failed to grok "monkey s*it". At the supply house, we also called it elephant dung. It was sold in 1 to 5 pound packages and looked like a gray turd.

When I worked in auto body repair in the 1950s, they used this stuff to seal holes in cars and it was called "dumdum". It seemed to have attracted a number of interesting names over the years.