I don’t anticipate that Statistics Canada will have these, but wonder if any institution has (and can share) digital boundary files for the 1992 provincial ridings used to report the referendum results. I have checked at <www.electionsquebec.qc.ca>, and don’t see an option to download the files from there.
Failing that, are paper copies of the 1992 boundaries available?
Have you checked the ISQ website? They seem to have an open data portal
I checked a couple of entries and they have contact information - it may present a lead.