The original DVD image (iso) can be downloaded as torrent:

[Only registered and activated users can see links. ]

I assumed the DVD ISO and the img would cover the same area but I think I was wrong: the SD cards are covering a smaller area but some of them have the same name as the DVD version.

There are 6 DVD's covering entire North America.
There are 12 SD cards covering North America:

[Only registered and activated users can see links. ]