I have had decent luck with bicycle cable at the carb end, but the knob end will not work at all.
"Universal" choke cable is available in custom lengths off rolls similar to tubing, rope or any other wire. I'm sorry, I can't remember the source's name but I got some (for a different project) from an industrial vehicle repair shop.
Get a very long piece, pull the cable from the guide (armor) and cut suitable lengths with a hack-saw or small cut-off tool. Once the armor is properly sized (and de-burred), thread the inner cable through and perform your loop. The stray ends can be lopped off once they have been threaded through the stops on the carbs.
A dry-film lubricant is a very good idea. Grease works fine but tends to leak out at inconvenient places!

Mike!