I was shopping for a 2.5 lb. unit for my car a couple of years ago and ran across the following supplier:
Dave Williams
Kansas Fire Equipment Co. Inc.
Phone: 1-800-262-8943
Fax: 1-316-264-4461
www.kansasfire.com
Dave recommended Halon and I bought a chrome unit from him for just over $120. Not sure of the price now, but his price was very competitive in July 2005. There were cheaper options, but he definitely recommended Halon over Halotron and other options. He was very knowledgable, so you might want to give him a call.
Good luck!
Chuck