After writing a piece for Wikipedia on Austrian flags, I have seen a few comments about surviving examples. I had thought that just four had survived the burning of the Grande Armee and earlier trophies, two having been in Charles Vernet’s studio at the time. They are a white Leibfahne and three yellow Ordinarfahnen, all of the 1792 pattern. Then I came across Edward Fraser: The War Drama of the Eagles (1912). https://books.google.com/books/about/War_Drama_of_the_Eagles.html?id=hEdwCwAAQBAJ
He says that 45 Austrian flags taken at Ulm plus five unspecified others are still in the crypt, but have only been displayed at Napoleon’s reburial. The trophies of Austerlitz were hastily taken, down in 1814, but apparently vanished. At the Luxembourg palace were 110 trophies, which the French then forgot to take down after Waterloo. Consequently, 59 were taken back to Berlin (and presumably lost in WW2), while 51 were hidden and later sent to Les Invalides.