A used Acorn stairlift is available for free to someone who is willing to collect it. The stairlift is currently fitted to the left side of a staircase which has a 90 degree curve at the top.
It has modular pieces, so could be refitted only using its straight section. or other pieces could probably be added from the manufacturer to make it fit to a different (left side) stair.
The straight section of the stairlift is 8' 6" long, and with the curves the full rail as it is set up now is about 18' long. It is not new, probably 10 years old, but in good working order and was serviced regularly.