Not a lot out there. The problem with temperature data for lakes is how you measure it. Surface temps change daily depending on sunlight, rain, etc. Plus, you have to find someone interested enough in the data to want to fund it.
Believe it, or not, this site and the old FB are my go to for finding water temps on different bodies of water. Pretty much all modern electronics have temp options on their displays, so asking for specific locations has worked the best for me.