Hi there, I am a big fan of the Prometheus and Alien Art direction and I like those bridge chairs in the tradition of the original Alien and I will try to build one myself. According to the designers at the Shepperton Studios the Prometheus chairs were build on top of existing truck chairs. Unfortunately, they don't remember the manufacturer anymore. I have not had any luck in identifying the frame underneath but if you know the brand would be very helpful. There is one at the Propstore for sale. Thanks
http://www.propstore.com/product/prometheus/prometheus-bridge-chair/
http://www.propstore.com/product/prometheus/prometheus-bridge-chair/