Kasentex via Amazon has 16×24" Kasentex Adjustable Soft Fluffy Sponge Foam Waterproof Pillow for $89.99 – 25% when you clip the on page coupon + use code 50ESFBGP to drop the price to $22.49. Shipping is free with Prime or orders of $25 or more.
https://www.amazon.com/KASENTEX-L…B09FYD11Q4