Hi Lee
I think the 959 is a 10mm steel axle, which makes the solution easier.
We have a drawer of shimano freehubs new and old and can almost always find something.
First you want a visual match. Then check the fit is ok.
Then you need to fit the freehub body onto the axle/cone&locknut assembly and check the axle projection is correct, I.e same as before.
If not, you might need to change some spacers.
Most shimano hg freehub bodies (10mm steel axle) of this era are interchangeable with little or no work.
Your cheapest option would be to find a hub of the period lx or above and try swapping that, if you dont have a shop like us nearby you could take it to.
Tom
Bristol