Go to a motorcycle shop and try on a few different makers, the fits can differ.
The new carbon fiber helmets are lightweight but they get pricey.
Most tracks/events now require Snell MA or SA 05 or newer helmet. The 2000 helmet may not be accepted. Of course a shop shouldn't be selling them either.
Here's a really nice helmet, something tells me it's an expensive one.
Here's a good selection, you can get an idea of a few options.