It's very easy to find accounts of flying serpents and dinosaur-sized reptiles, written by historians considered otherwise credible and sometimes even from a first-person perspective.
I have been completely unable, however, to find any supposed eye-witness report of a reptile that breathes fire or smoke, not even a tiny, wingless one.
Is this because there aren't any?
Any report, no matter how fictitious, will do!
Kinda.
In Serbian folklore, bolides were described as fiery dragons, that fly across the sky with fire pouring from their bodies. You may find eyewitness accounts of fiery dragons in Nenad Đ. Janković: Астрономија у предањима, обичајима и умотворинама Срба, Belgrade 1951, pp. 130-134. Apparently there is even a contemporary account here.
However, Serbian dragon is not reptilian, but humanlike, sometimes with reptilian characteristics. Specifically, these fiery dragons are sometimes described as having reptilian characteristics. I guess that's close enough.
It would be interesting to find if there are Western/Eastern accounts about bolides and how are they described.
The entry for the year 793 in the Anglo-Saxon Chronicle famously refers to
fiery dragons flying across the firmament
However, whether their fiery quality is due to them breathing fire is not stated, nor is anything said of the witnesses.
The context is as one of a series of "omens" preceding a famine and an early Viking raid in Britain - on the monastery at Lindisfarne.