Hey, I might have something useful for this. I found some old Ultima Online ISO archives and uploaded them here(not mine):

https://drive.google.com/drive/folders/1Jw_QGpRJPGGnLUhYjVgk...

Not sure whether the exact files you’re looking for are included yet, but there are several server/client-era ISOs and backups in the archive. Might be worth digging through.

Let me know if you find anything interesting in there.