When you need a nap but reclining is not an option, the NapAnywhere Head and Neck Rest just might work for you.
A flexible 10 1/2-inch-diameter metallic alloy disc is embedded in soft foam padding. Using illustrated instructions, you bend and fold the disc's cantilevered "wings" in a way that cradles your tilting head, supports your neck and braces against your shoulder so you can rest more easily while sitting up.
Your shoulder keeps it in place by way of an included adjustable stretchable strap.
Info: NapAnywhere costs $59 and comes in crimson, cobalt, black, pink or lime, includes a carry sack, and weighs about half a pound.