Front splitter I call them but can be called valance, lips, spoilers, I've seen some nice Foresters with them on. I think you would need to get a Subaru Impreza or a Legacy one and have it fitted but could be wrong I will do some searching 1st
I did see this not sure how well it works but might give the look you want with less cost
http://www.ebay.co.uk/itm/SUBARU-FRONT-BUMPER-CHIN-SPOILER-VALANCE-SPLITTER-LIP-BODY-AIR-DAM-WING-/321200625932?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3AForester&hash=item4ac90c990c