JC Whitney carries 6 foot lengths of “Fresh Air Duct Hose” of an
appropriate size for the 120 FHC carb air inlet application. The only
problem is that, while it is wire reinforced and has a good black
fabric/tape weatherproof covering, it is not as stiff as the original.
However, I discovered that the duct could be kept from sagging by
slipping a couple of one pound coffee cans into it. (Yes, you need to
cut out both ends of the cans if you want the car to run :-)).
Today, there may be other sources but 10 years ago I couldn’t find that
sized air duct anywhere else… it has worked and looks just fine.