How about some quilted rice bags. I've heard that they are a big hit at craft shows.
http://frugalupstate.blogspot.com/2006/01/rice-bags-portable-cozy-safe-heat.html
http://www.allfreecrafts.com/sewing/ricehotpack.shtml
http://www.quiltbus.com/microwave-bags.htm
http://www.sewing.org/enthusiast/html/ef_ricebags.html