So I dug out this eBay link from another forum which seems to have some success:
https://www.ebay.com/itm/203496436505
I'm also now contemplating how to solve this problem myself as I'd like to enjoy my Cinema in a playback standard higher than 24/48, as the moment I run USB into a Schiit Etir then run THAT Coaxial out into my DAC and jRiver down-samples any blu-ray content into 24/48
So, I'll keep you guys in the loop on what I figure out, I may even pick up a Mytek DAC especially for cinema if it works best/better with the aforementioned conversion box