Hi Wahine,
DH just reminded me tonight that we know someone who breeds and sells Mastiffs. We bowled with them for about 3 years. Great people, Deanna & Scott. If you contact them, tell them Edna & Dave from bowling say hi!!
I found info on them through Google when I couldn't find her business card.

Dewlap Kennels
Deanna Dallas
Portland
OR 97215
Ph: (503) 997-1380
ID: 5106