I found a source for HALON Fire Extinguishers (for aircraft):
http://www.sportys.com/acb/webpage.cfm?&DID=19&WebPage_ID=68

$51.95 to $150.95 for 14 oz. to 3 ½ lb.
from SPORTY'S 1-800-LIFTOFF or 1-513-735-9000

-Larry