For reference, in case anyone in the future is interested, here is the information I have on this issue.
Opcode Systems became defunct in 1998 (
https://en.wikipedia.org/wiki/Opcode_Systems)
The Roland SC-8820 sound module was released in 1999 (
https://en.wikipedia.org/wiki/Roland_SC-8850)
This perhaps explains why I can't find OMS Factory Names for the SC-8820, they would have to have been manually created by someone. Though it does seem strange that OMS installers exist without including a factory names document.
I did find this page (
http://www.andrelouis.com/qws/dlinst.htm) where the SC-8820 instrument names are in a text based document, but it's not the same format as an OMS Factory Names document. You can also find manuals for the SC-8820 which list the instrument names, but it's probably harder to extract the text from those pdfs.
If I have time I might create an OMS factory names document for the SC-8820, but otherwise I can still use the iPad Sound Canvas app in another mode and have compatible factory names in OMS/Cubase (eg. the SC-88Pro). If I create one I'll share it here of course.
As I write it occurs to me that I could search further for SC-8850 factory names (I understand the two models have essentially the same sound bank) and this yields forum post here (
http://macos9lives.com/smforum/index.php?topic=2813.0) with a tantalising web archived page link ... with a broken link to factory names for the sc-8850!
Oh, and I realise it might be borderline offensive on these boards to add an IPAD as a stand-in for a classic era hardware module but I'm just after a workable solution with no noticeable latency (my G4 quicksilver can't manage that on it's own) :-)