The cable comes from Lunashops and they are pre-built / already finished with different type of balanced plug and connectors, I just re-terminated one with a regular MMCX with the one shown in my picture. If you want a softer cable, I'll suggest their pure copper / OCC cable instead of the SPOFC cable I used. The MMCX connector itself is also easy to find - just search 'right angle MMCX' on most major electrical supplier (Mouser, etc) and you will sure to find it. They are however not designed for IEM but for its original application as WiFi connector, going mostly with very small coaxial cable like RG178, RG179, etc - and such they are a bit more difficult to solder then those intended for IEM and I'll strongly advise soldering iron with a very fine tip that is meant for SMD works. They are also designed without strain relief in mind, so you'll have to figure how you like to anchor the cable so they can withstand pulling as the soldering might fail if it is only point of contact between the cable and the MMCX connector. I used a combination of superglue and UV glue to permanently fixate the cable onto the MMCX connector, which you might have noticed on the close-up picture.
On a side note, I am actually building another one of this cable with the Sony 4.4mm TRRRS plug for another member, probably will finish sometime later next week. Will post picture of it once it is finished.