I'm currently preparing to get chinchillas have been adapting ways to cool them from what I've been using for my rabbit and hamster. These are untested on chins but work well for other small furries. A tower fan directed into the cage with a towel draped over the top of the fan and connecting to the top corners of the cage. It directs the air straight into the cage and can help keep them out of direct sunlight. A large earthenware mixing bowl in a corner with ice packs behind and/or under it. It will cool the bowl and they can lick the condensation off the packs without matting their fur. An ice cube or two in an empty food bowl. Quarter/half fill their drinking bottle, freeze, top up with water. Also, everyone here is giving solid advice, listen to them not me.