We have available the chair quilts for the UL camp chairs for both the low and high back chairs. They are made from ARGON90 and UP synthetic insulation. Up works really well for this application since is conforms well to the chair. The quilts have horizontal baffles to keep the insulation right were you need it and the draw cord makes sure it fits perfectly. Here is the vid and link...
https://dutchwaregear.com/product/up-chair-quilt/
UP-chair-quilt.jpg