My neighbours fixed this by just having an old freezer in the garden filled with water. Apparently that works because the freezer is under outside circumstances mostly unable to get the water frozen completely so they just used a hammer to destroy some of the ice and then plunged in. It's of course not super clean after weeks of use but it's at least cold enough to ensure the water does not accumulate any bacteria.

I don't know how they did it in winter but i'm sure it could be sort of regulated with a simple timer attached to the power supply.