There is a photo of the 1/4" F6 techflex in this post from the Team thread, http://taperssection.com/index.php?topic=153650.msg1976262#msg1976262
I also thought it was too bulky. I tried the 1/8" F6 with the Naiaint X-X cables and it was a really tight fit. The two cables didn't really let the techflex fully surround them.
Now that I am thinking about your goal, have you tried the regular 1/8" or 1/4" techflex? If you were to unplug the cables from the body, then slip the binders, one right after the other, inside of the expandable braiding, you might be able to fish both through and get the cables inside.
I did this with a pair of Countryman B3 mics that were terminated to a single 1/8" stereo plug, but the capsules are smaller than the binder plugs, and it has been awhile so my memory of how I did it is a bit hazy. I may have used some 9/64" brass tubing to slip inside the techflex and expand it, then put the capsules inside of the tubing, slipped the length of tech flex I wanted over the tubing onto the cables, then removed the tubing from the techflex. You might be able to use a plastic straw that could be cut away later. That might be enough to get you started. I can check to see if I have some leftover techflex in my bag o' stuff.