sonybookid: identifier defunct?

I'm trying to clean up the identifiers in my libraries, get them down to just the ones that work as links from under 'Ids:' on the book details panel. I have a load of books with just sonybookid identifiers in the format:

sonybookid:CBUSCEHCH026HH0F

I see the Sony ebook store closed down and was taken over by Kobo. Can these identifiers be converted to something that works, or will I have to run the metadata download to find working identifiers for them?
Thanks.