I also purchased that FiiO short cable and have been using it for a day or two. It is 45 cm in length and is long enough to allow freedom of movement when I have the ES-100 attached to my collar, but not too long where it is a nuisance. Microphonics are not an issue at all. For the money it’s not bad. I would prefer to have a shorter version of the cable offered with the FA7- shown in the pic below since it tangles a lot less.
I also have the Fiio BT cable- black cable shown in the pic. I love that cable since it is compact, easy to use, but obviously does not connec to the ES-100, but it sure is convenient.