For those above mentioned HJC helmets, I do not believe they are SA (Snell Automotive) approved rather SM (Snell Motorcycle). They have a specific section of their website devoted to AUTO and i believe those ones that specifically state the SA2005 are such.
I have also had good luck with the following website and have ordered from them.
use coupon code bimmerforum-10 to save 10%. found that googling their coupon codes.
I ordered the zamp fsa-1 helmet as a track helmet. I also hoped this could serve as a dual-purpose helmet for my bike as well. I am happy with it as an auto helmet but for bike use it has way to much wind noise for my prefference (creates a high pitch whistle). This makes it hard to find a dual purpose helmet without actually being able to take a test ride in one.
hope some of this information was of assistance
Nice find, Dan.
For what it's worth I believe the Scorpion EXO-400 is approved and is about a $140 helmet. I had one save my life during a highway-speed get-off (landed face first) so I can personally vouch for their quality.