You can save gallon milk jugs fill with water and freeze then cut them apart when ready to use. Then toss the cut up jug in the recycle bin. Need to let them sit for a minute then use a carpenters knife.
It's surprising how fast the return water melts ice. I stick with the CF chiller but some years the ground temp gets high enough in mid-late summer it doesn't do the trick. I put my IC in one of those storage bins with ice and pre-chill the tap water going to the CF.