There seems to be broad agreement among experts that bats are the primary reservoir, and less agreement about an intermediate reservoir (although pangolins are commonly proposed). We certainly have wildlife sequences from bats that are plausibly recent close relatives to SARS-CoV-2.

As far as the Chinese lab goes, I suspect that any research they release or international inspections they allow would just be dismissed by many people as evidence that they must be confident in their ability to cover up the horrible things those people have already concluded without evidence.