Techart did one from what I remember. This is a UK distributor but will give you an idea of what's available http://design9114-px.rtrk.co.uk/fu/pt715_-cma81-cmo82/Porsche/Boxster/Spoilers---Body-Styling/
Loads of different styles available from bumper changes to complete body kits. Quick Google of "Boxster GT2" brought up lots of sites also, I'll let you search through all of them