I found a fitted cot sheet for camping and RV cots that fit a smaller mattress normally used when back pack camping or RV bunk beds that I really like.
Fred and I built a small toy hauler that utilizes bunk beds to save space. The small mattresses our bunk beds use are roughly 27 inches wide, 73 inches long and 4 inched thick. These fitted cot sheets are ideal for our application.
If you use a fitted cot sheet that you really like and that's different than these, please share your link in the comments below.