Where can I purchase replacement rigging for Vintage cat

I'm the owner of a vintage cat (Taft Flying-T) https://www.thebeachcats.com/pictures?g2_itemId=131953&g2_GALLERYSID=b800ce7d2c526c244e2e35d95f196d41. I had a rigging cable fail and need to replace all 3. Any advice on vendors or process for measuring accurately?