My backup N900 is practically new. Now, I don't want to give it away, but it has a German keymat which I detest for its lack of four proper cursor keys.
So you could broaden your search for N900s with English keymats in good condition and if you get one, we can swap keymats.
I must say though, that I've never taken an N900 apart. I believe I've seen a video that showed that swaping a keymat is not that complicated, but I'd have to refresh my memory on how to do it exactly.