I made a pretty determined search as well with no luck.
I have a waxed, flat cord that is used for whipping rope work - knots, spices, ends, etc. The cord is flat because individual strands are not twisted together and the wax is required to hold the united strings to make a cord. I've never see flat lacing cord but assume it is made the same way. Remove the wax and you quickly have a mess on your hands. Much like unwaxed dental floss.