By way of keeping up to date, the available options for sitting off the ground seem to be as follows.
I've set a weight limit of not much over 1 kg, not listed generic copies, and excluded anything that depends on something else (such as a tree)
Helinox Chair One, as up thread, 960 g, 145 kg weight limit
Helinox Chair Zero, similar, a bit lower, 510g, 120 kg weight limit
Helinox Ground Ground Chair, 640g, 120 kg limit
Alite Mantis, 825g, 120 kg
Alite Monarch rocker, 590g 120 kg
Alite Mayfly, 173g, 120 kg
(complete with 4th July offers)
Thermarest Uno Chair 990g, 113 kg limit,
£59 at presentAlso doubles as a table
Thermarest Treo Chair 1040g 113 kg limit
The Robens range Geographic (tripod): 260g 120 kg, 23 cm high x 28 cm across
Geographic High (tripod): 340g 120 kg, 32 cm high x 33 cm across
Hiker: 999g, 120 kg
Pathfinder: 990g, 120kg, 46 cm pack length