My 'cool' area was supposed to be my garage but when checking temps recently, it has been sitting at 20C-21C during the day. As I have the space in the garage, I bought a cheap £20 fridge on Gumtree and have it plugged in via a cheap timer which only powers it on for 15 minutes every two hours. Still experimenting with timings but at the moment seems to hold it about 12.5C
Alternatively, I was thinking about sitting it in a tray of cold water and using some of those plastic, re-usable, freezer ice packs e.g. put two frozen ones in the water in the morning and repeat in the evening. Maybe need about six so there's always a couple in the freezer ready. Or, tie them up and make a couple of cooler belts :-)
Like I said though - I have the space so went for the fridge.