Focus cam will fit on 4×5 Linhof Technika III. The leading edge will need to be filed down to calibrate for a specific lens. Follow this tutorial to calibrate the cam. This cam is available marked for 115mm, 120mm and 121mm to match the markings on your lens.
Available in Aluminum or Bronze. Either will work fine. Bronze is stronger, but costs more.
On demand printing and delivery of this item is provided by Shapeways.
Calibrating Technika Cams, part 1
Calibrating Technika Cams, part 2