"acétate d'éthyle"...i don't know the good word in english.
From brenntag.be CAS No: 141-78-6 - ethyl acetate (Not that much different to the French name).

I have found that it is often a waste of time talking to industrial suppliers when trying to find ingredients for old processes. Try instead, a specialist art shop that can supply raw ingredients to make paint in the style of Van Gogh or Picasso.

Nitro-cellulose varnish (lacquer) is no longer used in the quantities that it was and most people use an acrylic or polyurethane varnish - Neither of these would have been available to the Lumière brothers in 1903. It is likely that they used Shellac for the final coating.