What is the best water based product to use on your nose when using oxygen 24/7?

Humidification. No water based product in the nose is going to be very effective for very long. Much better to humidify the oxygen that you are breathing so that it does not dry the lining of your nose. Ocean spray nasal spray is a salt water solution that you can use without reservation if you cannot humidify the oxygen.
Saline gel. Saline gel is more viscous than saline spray, thus it will coat the nasal lining and have a longer lasting moisturization effect. The nasal mucosa can absorb the saline gel as it is water soluble.