Hi 911sc,
I did not lower the car. In Australia I have enough problems with curbs and speed humps already, so I didn't want to get any closer to the ground. I've been told by my garage that there is no additional strain on the wheel bearings. There are longer bolts on the wheels to attach them.
I got mine through a friend (off a 996), so I can't give you a name, but have a look at
www.fvd.de. They advertise wheel spacers in all thicknesses for all models. I'm sure they will ship them overseas, but they are heavy, so it will probably cost quite a bit. Are you in the US? Ebay seems to have complete Boxster parts sets over there.