You might be fortunate to get a liner, from a tackle shop, but bear in mind that liner will have fallen out of a rod ring...
They can be glued back into place, but it will always be a possible weak spot.
Reasons for them falling out are the rod ring guide has been bent, the liner got broken or chipped and cracked out.
The best solution is to replace the rod guide with a new one, and it is not that hard a job to do yourself.
Buy the correct size rod ring, and file and sand the legs down so they are perfectly smooth. With a scalpel cut the old whipping thread off the broken guide. Gently with wet and dry remove the old varnish from under the guide.
Whip new ring on. Clear nail varnish can be used to build it up, but a proper rod varnish is best.