At least in Toronto, N900s are not that difficult to find. There's maybe one for sale every few weeks, ranging in price from $20 for a non functional one to about $100 for a working one, but likely missing all accessories and even battery. The thing is they simply don't sell. So if you search every week or so, you WILL find one on kijiji.

Do not expect them to be in great physical condition though. Scratched digitizers, paint chipping on the keyboard, dents in the screen bezel and elsewhere are pretty much guaranteed. These are 5 year old phones that were used. Interestingly, every slider on these N900s works almost as new.

Good luck finding another one. It shouldn't be impossible.