As with any claim of possibility, it really comes down to whether we are able to measure it or not. Since we're not talking about quantum mechanics, this is not too difficult to speculate.
All celestial bodies I can think of rotate. The sun, the planets, the moon, the galaxies, clusters of galaxies, the supermassive black hole at the center if the Milky Way, accretion discs, etc. It would be very strange if they didn't. They couldn't even exist.
Indeed! There are lots of reasons to expect any astronomical object in the Universe to be rotating, e.g., because of the angular momentum it will inherit after formation.
Are there examples of non-rotating bodies?
IT is possible that an object is rotating so slowly that is is not possible for us to measure the rotation rate with empirical certainty, and so we may presume that the object is not rotating, and we'd be fine with assuming it is not rotating in our theoretical models of such an object (within that regime). I do not know of such an example, but one can exist in principle.
Here is a list of observed slowly rotating objects, i.e. asteroids and exoplanets. The asteroid with the currently known smallest rotation rate has a period of ~1800 hours, which is about 75 Earth days. As the first figure in that wiki article shows, there is no obvious correlation between diameter and period for exoplanets.
With disk galaxies, it is known that they all, regardless of difference in size, have the approximately same rotation rate.
Long period radio pulsars are rotating slowly compared to other pulsars, with periods of over 5 seconds, and they are very difficult for astronomers to observe. For example, PSR J0250+5854 has the slowest spin period when compared to any known magnetars and X-ray dim isolated neutron stars.
I can find no fundamental reason why such an object can't exist. Maybe a planet or two stars that have had a tangential encounter.
A simple answer (perhaps) is conservation of angular momentum: the progenitor's angular momentum before the object forms is not destroyed.