I'm using the Nutshell Leather belt case originally for my old Treo 650 for my new n900 and the loaner before that.

Special bonus: the headphone hole cut for the 650 aligns nearly perfectly with the headphone port on the n900. And the top strip is thin enough to allow charging while closed.

Not sure if it's changed since I bought mine (3-4 years back)
http://www.tuff-as-nuts.com/treo-650-belt-case.html

Been quite happy with their cases, also got a case from them for my aging Zaurus SL-6000 5-6 years ago; both are still in great shape.

Will try to get some pics later.