I have frequently called summer a long disease that has to be suffered through -- and I meant it. But I do like the challenge of escaping scorching sunlight and summer heat.
It is perverse how a person can be pulled in the direction of solving their problems by spending money on gadgets. It's true -- you could get lucky and the gadget might function a year or more, before it heads to the landfill.
But what are the alternatives to such uninspiring problem-solving? Most people suffer most from heat at night. Remember what it is like in bed in summer: your skin tries to avoid contact with other skin and with the bedsheets. I resent skin-to-pillow contact, and will sometimes sleep pillowless on my back.
Would it help to use a "water pillow?" I don't know if anybody makes something actually called that, but there are plenty of flexible water bladders sold in the sporting goods industry, made by Camelbak and others.
If ambient temperature water was put into these bladders and you used it as your pillow, would it help? Perhaps the plastic would feel disgusting next to your skin; a pillow case might take care of that. It still seems like that would be cooler than your neck and head lying on a thick wad of thermal insulator like a conventional pillow.
If needed, the water bladder could be put in the refrigerator during the afternoon to ready it for a cool bedtime experience.