If you're talking about a rear spoiler, then nothing available as far as I know.
The only one I've ever seen was on the Fox Marketing ISC (the green one). It was one-off, custom made/molded utilizing an aftermarket spoiler for an IS sedan.
2010 IS350C -- Obsidian / Black; luxury pkg SOLD
Mods: 19" ISSforged FM-8 w/ Michelin Pilot Sport PS2 | F-sport exhaust, intake, springs, shocks, sways, & **** | LX-Mode chrome handles | Sport Pedals | PIAA Yellow fogs
And no, it's not an F-sport
2006 IS350 -- Blue Onyx Pearl / Sterling; premium pkg SOLD