OK, just to put this to bed once and for all:
The engineers I just spoke to at Sennheiser said he very much doubts custom cable would sell a copy.
The reason there's no logo on the casing is because the PH-ADAPT is a Service Part, rather than a full commercial product. It's supplied if needed when modifications are being made, but otherwise they are built to be made as part of another product (the MKE2 with XLR), so instructions are brief and logos deemed unnecessary.
Thanks again for help in all of this, another mystery solved.
