The smallest shelter kit I have come up with to date.

2 person AMK Heatsheet
36" of duct tape, folded flat
30' of decoy cord

If a poncho is needed, take a 12-14" strip of duct tape applied where you would want a head hole, then cut the hole in the duct tape/Heatsheet. The duct tape reinforces the hole. More duct tape will close the hole.
Or use cord to rig up A frame or lean-to shelter, tape for repair, etc