| What a lovely bike.
I had one of those.
The Marzocchi shock and forks on that model are all fully rebuildable.A reputable outfit like Maxton should be able to do this and revalve them to suit your weight and riding style.
If you want to go for a new shock,try Hagons.If they dont stock a replacement shock they can almost certainly make one.
If you are going to replace the forks then you need to measure the lenght of the forks,the travel of the forks and then the top/bottom yolk assembly.You would'nt want the front wheel hitting the engine under braking now,would you!
Personally,I would go down the rebuild route.The Marzocchis were superb when new and it could be the cheaper option.The bike also keeps the origional look. | 
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