Any suggestions would be appreciated ...
For starters, try Ferrari of Seattle; they might contact other dealers and arrange for a good one for you. Also look on ebay, autotrader and cars.com for another couple of dozen possibilities. I recommend only getting a 456M if you're looking for an automatic. Autotrader lists 7, 2 on the west coast, one blue, one silver.
"I heard there's rumors... on the... Internets..." about 456M s being everywhere for sale. Try Marshall Goldman in Ohio; Naples Motorsports in Seattle; etcetera. Go to Dupont Registry and do a search or look in the Ferrari Market Letter. Many automatics from which to choose.
The suggestions for where to look so far are all quite good. Get yourself knowledgable about the details of the cars, and the typical faults and expected maintenance needs of a decade-old car, so you can be well informed. This web site has some pretty sound information. There also are a few opinions here and there about problems that the poster has not experienced, such as supposed problems with automatic transmissions (not zero, but not of much concern in my mind [GM made the tranny internals]). The cars are a delight, but that delight would be reduced if you got caught out in repair work when it was not anticipated. For example, bad valve guides seem not rare, I found that problem on one car I looked at before purchasing another one. Also, let the M and pre-M styles sit in your mind a while. They are different outside and inside. You may well prefer one style over the other. Lastly, if you can get access to Mannheim bid prices, you will find that the lowest asking price cars out there should not automatically scare you away to the pricier cars. There is a range of understanding about pricing reality now. Some cars really are for sale, and some are priced without knowing where the market really is. It is a great time to buy. I've been very happy with my 456GTA for thousands of miles.