Huge fan of the thermarest ridgerest ones myself. You can't pop em, they are waterproof by their nature, awesome for sitting, and they rival the weight of most inflatables. They are not small and compact, but mine lives on the outside of my pack anyways, so bulk isn't a concern. Adding a second short piece would add maybe 5-6 ounces and would add more padding. You could tie it to the first full size pad with a few pieces of 550 cord so they stay together through the night.
The version with foil on one side helps the R-value a bit.