The K&N Airfilter is part 33-2784, may be difficult to find in the USA. Can be ordered directly from K&N at http://shop.knfilters.com/knshop/

The K&N Oil Filter is part HP-1002.
The Mobile 1 Filter is part M1-204.
The Purolator Filter is L20081 (or L14670).
The Wix Filter is 51348 and appears to be shorter and smaller which may make it easier to install.

The fuel filter can be hard to find. The FRAM G3829 should be a direct replacement and can be ordered off Amazon.

Replacement thermostat should be available at most local parts store, but tell them that you are looking for a 1980 Triumph TR7 (chances are they won't have a listing for the Esprit.)