This is intriguing.Maybe an entire suit could be devised using bird flu suits as a base:
http://www.sciplus.com/category.cfm/subsection/48044 LG. FLU SUIT
$5.95 EACH
Take two of them, nest them, and seal the holes with elastic, and inflate the space between with a flexible straw.
I suppose if convective loss due to open space in the air chambers is an issue, you could kill birds, pluck them, and stuff the down into the chambers...