Convergent design, or Marketek. I just bought a pair of 2 foot cables from Location Sound in LA. They are 50 ohm instead of 75, but two joined together worked just fine to a TV logic monitor. Haven't tested going to the Teradek Bolt yet.
I recently bought a few 6 foot 75 Ohm 3G Cables form Terry West, they are 2mm thick and work great with a Codex recorder in a backpack. If you only need 18" cable, Hot Rod Camera has some that are used on the Gemini recorder.