For the numbers, I think there is a company here locally that still advertises in the Rev record.
For trying on a helmet, if you are going the motorcycle (Snell M rating) I would try a big motorcycle store.
If you are going the racing (Snell SA rating) I would try one of the places in Indy (Simpson Store, Impact showroom or Motorsports Spares) or one of the Go Kart places (Comet Cart Sales just East of Indy)