Here are the two most popular web sites for the purchase of fire extinguishing products for RVer's.
Mac The Fire Guy Products.
Fire Fight Supplemental Halon & AFFF Fire Suppression Systems.
Look over what they offer and their prices then decide for yourself whether they are suitable for you.
There are also some very expensive fully automated systems for a coach but I have steered away from those due to cost, usually in the $5,000 - $10,000 range but still a bargain if it puts out a fire soon after it started thereby saving your RV.
Halon ONLY works in a small enclosed confined area. AFFF works the best in all other areas that are open with lots of air.
AFFF is similar or the same as to what is used at airports to smother fuel and other types of fires.
Water is OK but it's used mostly for defense and takes a long time to pour enough water on the fire to put it out.
The ABC chemical fire extinguisher that you typically find in a RV is not the best but it will work OK providing that they WORK when you need it. Most of the time the chemical is caked at the bottom rendering the extinguisher useless. I have allocated mine to living in my rolling garage for any campfire or BBQ problems.
I am by far no expert so it's best to talk directly to Mac to get all of your questions asked. I did back in 2009 prior to leaving CA for extensive road travel.
There is also a member of iRV2.com named RVCruzer
who has written up a great article about fires and types of fire extinguishers, etc. I would suggest everyone spend sometime and read through what he has to say. Some people, mostly the skeptics, could possibly learn something.
I have not been sorry for one second investing into the fire suppression systems that I now have installed in my coach and truly hope that I never see the day that they are needed.
Dr4Film ----- Richard