A friend of mine who needed a chiller, he used a mini refrigerator. He
drilled 2 holes in the side of the refrigerator, He used filter tubing,
rapping it around the freezer coil several times before the water returned
to his tank. If he needed the water colder, he would add more tubing around
the freezer coil. It was a hit or miss process until he got the proper
length for what he needed.
What I can not remember is if the tubing, on one end was hooked to his
filtration system or if he used some sort of power head to move the water.