The image intensifier used in this project was sourced from www.ebay.co.uk and entering "image intensifier" into the search box.
The photo below shows the P8079HP Generation 1 Image Intensifier
The image intensifier is a P8079HP generation 1 ex-military version. It operates on 3-6 volts, is 18.5cm long, housed in a 6.25cm diameter tube, with 20mm optics.
The P8079HP Image Intensifier showing the sensor window.
Other image intensifiers will probably work but we have not tried them. It is likely you will need to make simple modifications to instructions to use these various alternatives.