In English, “un collier pour badge” is usually “a badge lanyard” or simply “a lanyard.”

Common wording

  • Badge lanyard : the most specific and natural term for the cord worn around the neck with a badge holder.
  • Lanyard : common if the context already makes it clear it’s for a badge.

Example

  • “Could you give me a badge lanyard?”

Small note

If you mean the plastic holder itself, English speakers may say badge holder instead.