I've been shopping for a Halotron extinguisher and stumbled on these from Zoro at a great price $78.15 with free shipping and no tax. Comes with a wall bracket. Vehicle mount is $8. I've got a couple on the way.
http://www.zoro.com/buckeye-fire-extinguisher-2bc-25lb-cleanagent-70258/i/G9783295/
http://www.zoro.com/buckeye-fire-extinguisher-2bc-25lb-cleanagent-70258/i/G9783295/