It's a bit bulky but any kind of ensolite pad, like a Thermorest Z Pad or a cheap 3/8 pad from Big 5 or Walmart, on top of any other pad will give you some very useful extra R's. They weight close to nothing and don't leak.
“In a time of deceit telling the truth is a revolutionary act.” ― George Orwell
It's not over when you lose. It's over when you quit.
