Could you remind us what the "non-lab-leak scenario" is again?
To be clear, is your "likeliness" determined on whether we can find a creature that is more similar to covid than RaTG13 (we haven't) or something else?
The non lab leak scenario is just what it historically has been for ~70% of all viruses that we can trace (and probably the remainder as well, but we have no evidence): zoonotic jump.
The lab-leak scenario presumes zoonotic jump, too. Just rather than from something in the wild, it's from humanized (ACE2-transgenic) mice, which WIV was known to be using to study SARS-like Coronaviruses.
The coronaviruses being studied at WIV included RaTG13, one of the closest relatives (96.1% genomic match) to SARS-CoV-2 ever found in the wild.
But a key difference between SARS-CoV-2 and it's wild relatives is the spike protein with affinity for the ACE2 receptor, so it would have had to have evolved through an intermediate host with a human-like ACE2 receptor. For example, ACE2-transgenic lab mice.
This does not itself rule out the wild-origin theory, but no wild host that could explain the missing link from RaTG13 to SARS-CoV-2 has yet been found.