I used a little
https://www.amazon.co.uk/Hermetite-R.../dp/B0068PMBR6
clear silicon would do the job I imagine and you'd need to take less care avoiding red compound being visible!
I was fitting new ones after managing to smash mine in a crash so was more concerned about the two parts not being simpatico. You probably can ordinarily reuse them but the ones on your bike must be about 20 years old, I imagine the material's lost some of it's malleability .