They can be found on ebay and amazon. I paid $5 for a bag of 10, with free shipping from US seller.
![Image](http://i58.tinypic.com/3178hma.jpg)
They crush and seal nicely without being over-tightened.
![Image](http://i62.tinypic.com/2ecj7ft.jpg)
And they fit the drain plug well.
![Image](http://i61.tinypic.com/311vuqv.jpg)
A bag of 10 should last 10 yrs or 80000 miles, per the manual.
I've used 5 in 7 mos & 3200 miles.
Fish