Aloha Frank,
Seats components are available from Moss and probably also from Victoria British or The Roadster Factory. E-bay is also a good source to look for these parts. Hemmings Motor News can usually be found in most mall book stores, it lists lots of smaller parts suppliers that could be helpful to you.
If you still have the temperature gauge, there are several places to get it repaired such as Nisonger Automotive. An alternate is to use an electric gauge from a TR 4, but you will also need to add a voltage stabilizer to the circuit. The voltage stabilizer is available from Moss, etc for about $15.
Safety Fast,
Dave