Online, hard to find local. Try friends/forum members in your area and try on for size. I was fine ordering online since I went with the GP6 and have had GPs for the last few series and was comfortable with the fit. Try ordering from Apex, they are very friendly and can get either Stilo or Arai with good prices.
08 E90 | Jet Black / Black | 6MT
Mods: RAC RG63 w/ Pirelli Corsa 255F/285R | Akrapovic Evo Exhaust | OEM Blacklines
Winter Setup: OEM 18s w/ Nokian Hakkapeliita R 245/40-18