If your canoe hatch has disintegrated or perished it is more than likely a Valley Canoe hatch. KajakSport Hatch Covers are a perfect replacement that does not perish.

They typically last 6-10 years. 

Available in Oval and Round

Measurements:

OVAL
LENGTH:    External Edge  - 475mm
                    Internal Edge   - 425mm
WIDTH:       External Edge  - 285mm
                    Internal Edge   - 240mm

ROUND
    External Edge - 230mm
    Internal Edge  - 240mm