A bit of digging around this morning has uncovered a digital copy of a French translation in the Bibliothèque interuniversitaire de santé (Paris)]:
* 1545: L’art de memoire qui est aultrement inscript le phenix livre treffort utille & profitable a tous professeurs des sciences, grammariens, rheteurs, dialetiques, legistes philosophes & theologiens
Given the date and the scant 16 pages, this is likely to be the edition which was the source of Robert Copland’s English translation. As the edition doesn’t appear to have an author, it’s possible that this was the reason that Copland’s translation didn’t list one either.
The Latin -> French -> middle English -> modern English route seems an awfully muddy way to go, but without anything else, it may have to suffice for some of us for the moment.