I believe you are referring to the tendon that has the loop on the end to pull for shifting?
https://www.hobie.com/support/Any MD180 model:
https://www.hobie.com/support/mirage-sport/http://static.hobiecat.com/digital_assets/MD180_PARTS_GUIDE_DHWb0tr.pdf81486001 HANDLE & TENDN MD180 FWD
81000801 STICKER - FWD, GREEN
81491001 HANDLE & TENDON MD180 REV
81000901 STICKER - REV, RED
81493001 LEVER SHIFTER RIGHT / REVERSE
81496001 LEVER SHIFTER LEFT / FORWARD
Likely you would have to replace the shifter as well. This should all be covered under warranty, so see your dealer.