Digging around on Yahoo Japan Auctions I came across the Logitec (yes, no "h" it's not the one you are thinking of) LCW-T1210BSU an intriguing looking CD-RW unit that supports both SCSI and USB. This particular auction was for a pair of them and did not seem to be evincing much interest, but was priced a lot less than the straight out adapters. Thinking this could be a way to get some adapters cheap I set out to do a bit more research.
Thankfully Logitec still have a drivers page for the LCW-T1210BSU online, and poking around on that it seems the CD-RW drive is actually a [TEAC CD-W512EB], which is an IDE drive so it seems this Logitec case must have both a USB to IDE and a SCSI to IDE adapter within it. Considering that modern USB to IDE apapters are very cheap I think it would only be useful for someone who needs a SCSI to IDE adapter, and it seems like it might be fairly custom, so no luck for me but perhaps useful to someone.