It might fit. I can tell you that the N810 doesn't fit in the Urban HipHolster, but that's a nice product too. As an off-topic FYI, it looks like the pen holders on most of their products are the same size as my HipHolster's, so if you get anything from them, check out the Zebra-brand aluminum collapsible pens - they're fairly nice, but you can buy them at WalMart.
To the OP: I'm sure some people would find an armband useful, but I've never used one for anything, and I'm curious what the advantage is over a belt holder, or something else. I would think that waving the headphone cord around trailing behind your arm would be less convenient... enlighten me...