The coolant bottle has a crack in it cam I fix it or have to replace it? on 1990 Cadillac DeVille

Just noticed the crack in the white coolant bottle today has very little coolant in it.thought I saw a wet spot under my car the last time I drove but can't get the cap off the radiator to check the level in the radiaator. Help anyone please I'm ole lady 76

Asked by for the 1990 Cadillac DeVille
Usually this can be repaired with 5 minute epoxy available from any hardware store, But it has to be clean and dry