Ex mil stuff needs research before buying.
Some of the curent kit is quite light (value for money) but you can go lighter at cost.
Seen some tarp/bivi/ponchos in the 400-600 gram area, i still have my old 1980’s MOD poncho, weighs in about 1 kilo, my Terra Nova tent which sleeps 2 in midge free dryness luxury is about 1.3kg at minimum weight.
Haven’t handled a current spec MOD Poncho, but as already stated they are tough and multi use, my old version doubles up for stretcher and bodybag duty, can be poppered up one side for a crude bivi bag affair but non breatheable. Keep the nuclear fallout off you as you sleep 🙂