It's possible to buy 10% buffered formalin on UK ebay.It probably contains the 37g/L paraformaldehde required to make D-85:
However it may also contain 4g/L mono- and 6.5g/L di- basic sodium phosphate which may affect the pH,so it would be an experiment.
The sodium bisulfite in the formula could be reduced as it is a pH reducer like the phosphate already added, and probably just a preservative.