Here is a spare part source for the N900 and other Nokia models:

http://www.klc.fi/fin/tuotteet/Nokia-Varaosat-N900

I currently have an order in transit for a new battery cover amongst a few other things.

The N900 camera lens cover is apparently made up of several components. The Carl Zeiss tab recently started peeling back on my 7-week old device, and now I have what looks to be a spring sticking out the side of the lens cover. And of course the sliding door is now malfunctioning.

I'm in Canada where Nokia refuses to do anything for N900 owners. It has been major aggravation dealing with Nokia USA on this matter. I think Nokia has failed in this regard, but I digress...

So far KLC has been great. The ordering process was impeccable. Package should be arriving soon...

Happy N900 repairs!

UPDATE: Express order placed Tuesday night and received overseas Friday morning! Everything perfect... highly recommended