What stinks?

something has been smelling real foul and sour by my desk for the past 2 weeks. It smells like dirty socks and I can't figure out what it is because only a random whiff or two hits me every now and then and leaves me searching. At first I thought maybe it's me, I'd smell inside my shirt, socks, armpits, but nada...

You see, couple of years ago I had the same problem and it turned out to be the leather band of a wrist-watch I wore hiking everyday, it was rotting with the help of my sweat and I could only smel it when I had my left hand suporting my chin when I read articles and junk but I'm not wearing a watch anymore...

I remember last time I had the delima for a few weeks too trying to pin-point the darn smell, this time I've smelled everything, the mouse pad, the keyboard wrist pad, even the canvas on the directors chair I sit on, but no luck so far...

Wish me luck and I will inform the inquiring minds when this mystery is solved, thank you!