Update:
I did purchase the headmaster. I've not had a whole lot of luck with it. It feels good at first, and then after about 15 minutes or so, I want to rip it off. If I let my chin rest on it, it puts so much pressure on my teeth. I think if I had a gel tooth guard thing, that might help with that. (but I don't, as yet anyway)
Ann (Abbas Child) suggested I try an inflatable type, and posted via a private message the link to an internet seller. It cost about $30, which is roughly 1/4 what the headmaster did. & I like it better. I keep it in the car, because this is the activity where I feel the most stress on my neck. Its not even close to perfect either, but it seems to help more than anything else so far. Its such a trade off as far as comfort goes, because its softer, but then again, its hotter to wear. What works best (when I am the passenger, of course) is to recline the seat back, and with this inflatable collar on, my head doesn't do too much bobbing around. Sitting with the seat back in its full upright position (can you tell I was a flight attendant ? lol) it doesn't really help as much as I would like.
For those of you who are CALS, you may wonder why your PALS is not more receptive to wearing one. All I can say, is I am amazed at how uncomfortable any device is that holds my neck and head into a certain range of motion. (who knew?) I really feel for the whiplash victims of the world now. I've only tried the two styles, but, with each type, when I first put it on I'll think it will help so much, but in such a short while I'm ready to take it back off again. The softness of the inflatable style is nicer as far as the "clenching the teeth together" aspect though.
If you are interested in looking at the type recommended to me by Ann, do an internet search for inflatable cervical neck traction.