I think the answer is that no observations have yet been achieved of objects outside the solar system providing sufficient information to suggest habitability for any period of time at all.
The only candidates are planets. A large, dense gas cloud would either have so little gravity it would quickly dissipate so as not to be breathable, or enough gravity to collapse into a gas planet. Realistically some rock would get included to and you would have a gas giant or ice giant.
Many exoplanets with masses comparable to the earth have been discovered. A fair number of those are thought to be rocky and close enough to a red dwarf star so that the temperature, at least, should be reasonable. Ones in the habitable zone of sun-like stars are less known because it takes longer to observe enough orbits to detect them.
As far as I can tell, spectroscopic analyses of exoplanet atmospheres is only just beginning. I believe discovery of oxygen in an exoplanet atmosphere would be big news, and I have not heard of it happening. For instance, this NASA site only mentions detections of helium and water vapor.
Even if oxygen were detected, the atmosphere might be much too thin. It is almost impossible to estimate surface atmospheric pressure of a rocky exoplanet; I think you would have to directly observe the thickness. We are not close to being able to image exoplanets with that kind of detail.
A medium-mass, low density planet can be assumed to have a thick atmosphere that would have an earth-pressure level. If oxygen were detected spectroscopically on such a planet, then it would be a candidate.
To summarize, the best candidates would be an earth-sized rocky planet with known oxygen but unknown pressure, or a larger low-density body with known oxygen and a likely altitude with suitable pressure, but no surface to stand on. But no such objects have been found. Yet.