I am also looking for a suitable stylus to replace the cheap plastic one that comes with our beloved N900. I so miss the quality of the N800 one...
So far I have bought two different ones on EBay. One is practically all metal and is also telescopic, but has to be unscrewed to be used and it hangs from a lanyard, and that makes it less than practical, thought it is still very nice indeed. The other is the one from the N97.

An all metal or wood stylus with a plastic tip covering would be fantastic. For it to be perfect, however, it needs to fit into the N900 stylus receptacle. If you make one, please let me know. I will buy at least 5.

Oh! Make it Bluetooth also. Because everything can be made better if you add Bluetooth to it.