@whitequark I have a couple of nice little 24V centrifugal pumps with BLDC motors with a little speed controller in a box with a pot to adjust it. A Chinese friend ordered them, about 12 years ago. It won't self-prime, so it should be located below the water level (or below any possible air bubbles, even if there isn't supposed to be air).

They are about fist-sized, and waaay too powerful for what you want, I think. They make a fountain comparable to a garden hose at full power.