I backed the passenger side tow mirror of my 2007 Tundra into the side of the garage, and broke both the large top mirror and the small lower mirror into several pieces. The tow mirror housing itself was not damaged.
The parts people at my Toyota dealer said that the small mirror was not available as a stand alone part from Toyota although the large mirror was available for $27. It was their opinion that mirror glass was not available from anyone.
They wanted $850 for a complete new OEM assembly plus $100 to install.
After searching the web, including e-bay) I located several 3rd party after market, non OEM, mirror assemblies for much less and ended up buying an OEM assembly from TRD Sparks.com for $350.
About two weeks later after seeing an add on the web I discovered that mirror glass was indeed available at: Car and Truck Side View Mirror Glass Replacement - Home
At least I will be ready for next time.