if you want really thin, and for a short length...i'd make it myself w/26awg conductors, twisted in a thin copper shielding. then techflex it. that would be a good one.
but, from my stock. I'd use 24awg twisted pair. Its much stiffer than the normal cheap black wire you see attached to most stereo mini plugs.
But, it passes electrons like a mo'fo', and thats what its all about !
I found the locking stereo plugs for the DPA MMA6000 and picked up a few. If anyone else would like a custom locking cable for the MT or R9 / MR-1, just ping me. I'm workin' for cheap these days, trying to get rid of inventory to start fresh.