Swimming Pool Supplies, Pool Safety Cover, Swimming Pool Covers, Swimming Pool Pumps, Pool Pump Parts - INYOPools.com
They have AWESOME CS and have helped many people with pool parts such as this. Make sure to tell them TFP sent you for the white glove treatment!
I believe it's a Hayward light based on the stainless face ring. Just take the gasket up to Leslie's if you have one close.