If you want a leak proof cooler, you may have to spring for a roto molded cooler. They ain't cheap though. One that might be affordable is the 30 quart Engel cooler/dry box. It is $64 on Amazon. It has a rubber gasket and latches and should prevent spills. I use it in my boat as a dry box, and it keeps the water out, so I assume it will keep the water in as well.
https://www.amazon.com/dp/B00MQ1QY92...ing=UTF8&psc=1