I took a memory foam pillow car camping once to one of the Overland Expo's, I found out when it got cold, the foam got hard. The next day I bought a Nemo Fillo inflatable from one of the vendors. It isn't inexpensive, but I have had it for 5 years and I use it all the time. When not camping it makes a great rest for my laptop when I am sitting watching TV. It keeps my lap from getting hot too. It has some elastic on one side that you can jam a jacket or something to make it more full.I like twist memory foam pillow, its small, compact and very comfortable
https://www.nemoequipment.com/product/fillo/