I found what I thought was a nice item to experiment with, the Brunton "Lost Hiker Kit" which has a card with ground to air signals on it. These are consistent with:

CIVIL AIR PATROL U.S. Air Force Auxiliary
Mission Aircrew Reference Text
Volume I Mission Scanner
Revision June 2017
Section 4.2.3 Emergency distress signals, page 55.

The X indicating "Unable to proceed".

The kit is not bad, and it contains a signal mirror, a small disk compass that you punch out and then float on water (I haven't tried it yet), a fresnel lens, and some decent instructions. It fits in a wallet as the form factor is flat and the size of a credit card. It is about $10 on Amazon.