NHRA legal helmet, what do I need?

[fiveohpatrol]

I'll be goin to indianapolis raceway park this weekend to the first test and tune of the year (weather permitting).
The last time I was there, the track was slippery and I was running high 13's. He told me to get a helmet or slow down. haha, yah right like I'm gonna TRY to slow down

Anyway, I knew that I've needed a helmet for a while but they've never said anything so I'm gonna take one this weekend.
What do I need? will any DOT approved helmet work?
What about a motorcross helmet? a close friend has a few, one of which I could borrow.

I know I shouldn't skimp on safety but once my car is where I'd like it to be (streetable mid 11's) then I'll go all out with the safety equipment.

so what kinda helmet do I need and if I need to buy one, where should I look?
thanks guys (and gals)