Drop-in replacement elastomer rods for that fork (or really any of that era) haven't been made in decades. Some specialty shops may have NOS replacements in stock, or they may not. A Google search for "elastomer rods" returns many products that may or may not be modified to work with that fork. You'll need to match the dimensions and material properties to the existing one from the fork. As many have mentioned, that fork really isn't worth fixing and you'll be better served going with a replacement fork altogether. Note there could be other incidental upgrades required such as going with a threadless headset, and switching to v-brakes unless you find a replacement fork with a canti hanger.