You can get cooling pads which are sold for dogs but work pretty well for ladies of a certain age. They have a gel in which cools down under pressure. I had a fairly small one which I placed under the back of my neckOoh - I`ve found one that is actually intended for humanshttps://www.amazon.co.uk/2X-KEPLIN-Cooling-Gel-Pillows/dp/B07TW8QCSS
Pure cotton sheets and like @Missie they have to be white.