I just did a search on Toyota.com for "certified used" Prius in the USA. There are 80 2008's and 316 2007's available in the USA. The prices are all over the place and so are the cars. Make a deal on the phone and take a vacation to pick the car up. You can hardly go wrong with a Toyota certified used car. You can even still add the extended warranty.
It should be true that a Toyota extended warranty can be obtained at any time, until the odometer reaches 36000 miles.
Yes, I stand corrected as a Toyota can be a certified used car with up to 85,000 miles on the odometer and 7 years old. I thought it was up to 36,000 miles. Very few of these are over 36,000 miles though.