Since I've had my bike, it hasn't had the small o-ring for the oil filter.  I always seem to think about that right AFTER I finish buttoning everything up...    I'll be doing my next oil change in the next few days, and I'm considering getting an assorted o-ring kit from my local Autozone.  Assuming I can find one to fit, is there any reason one of these wouldn't work?

Did some looking to compare the dimensions of the stock o-ring to the assortment they had at O'Reilly's.  The stock dimensions are 2.4mm thickness, 15.8mm inner diameter.  The assorted individual o-rings were all SAE.  The closest was 3/32 thickness, 5/8 inner diameter.  Translate that to metric, that's a 2.3813mm thickness, and 15.8750mm inner diameter.  I can't imagine a couple of hundredths of a MILLIMETER making a huge difference.

For anyone else who needs this O-ring, it should be #114 at O'Reilly's.  All  said and done, I spent $0.65.  And, YES, it will be fine in the oil.  

::UPDATE::

I just put it on, and it fits just fine.  Nice and tight around the fitting to the filter, and it provides positive pressure when you push the filter against it.  Again, to any of you with PO's who lost an o-ring (because none of US have ever lost them, right?   )  here is the $0.65 answer.