I can't help you with where, but I must ask, why?
I can't watch videos from helmet cams. They wander all over and are so shaky that I have a hard time focusing on the images. Can't someone come up with a cam that mounts to the torso?
The cons out-weigh the pros I would say. Not to mention marking you as a fire j.o. That being said, equipment tends to get banged around during normal operations. If your cam gets damaged who is going to pay for it?
If you want to get one, the best deal I know of is to go to Promotive.com and sign up for an account (free). Once you have an account, you have to look for a team to join. There just happens to be a Fire and Rescue Team you can apply for. If you are an active firefighter, you should be approved easily.
I am pretty sure that the Epic brand of helmet cams is available to purchase at discount pricing. Be warned, there are a lot of other brands of stuff available through this site and it can be damaging to your credit card balance.
Live footage of incidents can be pretty jerky because getting footage should not be anywhere in your mindset while working at an incident. For training though, the helmet mount seems to work best since your focus can be on where your head is pointing. I use one all the time with pretty good results. One of the challenges is that there is no LCD screen so you can't go in and look at what you just shot easily. GoPro has a screen you can add. I figure it is no different than regular video shooting. It takes hours of raw footage to get minutes of useful stuff, but the right minutes can be invaluable.
All that being said, make sure you are aware of your department's policy regarding the use and property ownership of video and photos taken at an incident. A rapidly evolving issue.
go to firevideo.net, they have fire cams that are waterproof and heat up to 900F. I just bought the FC3 for $200 shipped to Canada with a blackjack mount to mount the camera to your helmet. The audio and video is great...when mounting the camera on the underside lip of the helmet, the camera will be upside down if you want to have the screw from the mount tighten on the flat of the camera and the on/off button easily accessible. I Just use movie maker to edit the video by rotating 180 deg and it works great!!
just bought the FC3 last week....it works great...not shaky at all, unless you are shaking from the awesome scene you are encountering!!! lol as long as the camera is securely mounted, you are good to go!!!