There were few brought into North America. But they are not very difficult to find. Not so many were actually sold, as the pricing point was never attractive. Most of them became dealership loaners. And if you really want one you can get a low mileage for about $40k. Dealers are getting rid of them as the main purpose was to advertise the diesel version of the car, purpose no longer in need as the line up does not carry 6 cyl diesels anymore.
As of today there are 139 2011 335d for sale in US/Canada and about 25% has the M sport package.