[rcheshire (Rowland)]

Jo. Ebay and several metal merchants and craft suppliers sell copper sheet of various dimensions. I used 1.2mm copper sheet to make a cold finger for a 1000D. Fits snugly between the back of the sensor and bottom of the sensor PCB, with a strip of packing tape for insulation from the PCB.

All of your metal junctions must perfectly flat and cleaned with very fine carborundum sheet to remove oxide. This will ensure the lowest thermal resistance possible. System performance is influenced by the sum of all thermal resistance, including the contact surfaces - sensor, copper, TEC heatsink. Use thermal paste.

All surfaces could be lapped, but I avoid doing this to the back of the sensor.

EDIT: Bending copper sheet can be done in a vice, sith surfaces protected by aluminium angle. Use a paddle to bend the sheet evenly with a tight bend. The vice I use, conveniently, has a 3mm recess on the top inside of the jaws. I use this with a couple of pieces of 8mm Aluminium bar and a small hammer to produce sharp bends up to 90 degrees, without compromising the flatness of the sheet.