We did a group buy on 5 lb. systems from Safecraft back in the mid-2000s on Spyderclub.com. I believe they were $325 shipped. I didn't think that was too expensive for the safety added. The system uses a cable pull to activate, and empties the bottle. The bottle appears to be a standard aluminum CO2 bottle, but filled to a much lower pressure with Halon. Today Halotron is used because it doesn't trash the ozone layer like Halon did.
I attempted to get it refilled(with Halotron instead) but my local place wouldn't/couldn't. I'll probably have to buy a new system for the new car.
I aimed one jet at my gas heater under the dash. There were two more jets, one at each carb up high under the clamshell, which should blanket the entire compartment with the Halon, hopefully snuffing it out.
The system was supplied with aluminum tubing, which was somewhat easy to work with and keep from kinking. I think it was 3/8" or so thin tubing.
I've seen modern racecar systems in the pits at Lime Rock using plastic tubing today. That makes me wonder why anyone would use plastic?