There seem to be a few different Troy Lee Helmets on offer at what seem good prices. An example:
Troy Lee D2 Piston Carbon Black Helmet 2010
The D2 Bicycle and Action Sports Helmet is the most technically advanced helmet of its kind. Astonishingly light in weight and incredibly strong, the D2 is the perfect helmet for BMX, mountain biking, and other action sports like snowboarding. All this and looks to boot, the D2 screams performance and style.
• Hi-Flow ventilation system
• TLD Orbit visor
• Titanium hardware (carbon)
• MX-Style padded liner
• Removable roost guard
• Carbon Fibre Shell
The best price I could find apart from this was was £250. RRP is £399.99 so it may be of interest to someone!