Very thin 4 wire cable

That type of wire is common inside headphones. You would need to do some searching and most likely it would be from a chinese vendor. Gore has some stuff and could make it but only if you need a lot.

A division of AKM has an elastic wire that may be a good fit if some stretch is needed.
 
Hi Peranders,

Here are a few manufacturers I've used in the past:

PVC Multiconductor Cable

Flexible Wires Cables | Micoflex Wire and Cable | Custom MadeFlexible Wire and Cable

MOGAMI® - Ultraflexible Miniature Cables

#2479 DAFLEX Ultra-Flexible FEP Subminiature Cables

Hope this helps!

-Len

I'm looking for a 4 wire cable with 1-2 mm outer diameter. Currents are in the mA range so resistance is of minor importance. This is for use in a product, not audio.

Does anyone have any source for this?