This used to be my dream bike (together with the Manitou FS). Unfortunately, not very many were sold and are still around. What did you do with the blue one?
And what happened to the top tube of the green one? Was someone looking for cracks?
I'm also 99% certain you could refill that shock with plain air. Remember, air is 80% nitrogen anyways. Nitrogen has the added benefit that there's no moisture in it, while normal air does have that. So if you would use air, you might contaminate the oil a bit faster.