Found a great deal this morning, figured I'd share. Mine are already ordered
 
LINK
 
M5x20 Socket Cap's for $0.01USD / piece while supplies last from Mr. Metric. 

Where do these fit? Do they replace the plastic windscreen screws?

Not a bad deal at a penny apiece until you factor in the $7.50 shipping. Of course if you buy in bulk, minimum $50 (5,000 qty) then you qualify for free shipping!  ;-|
 

Where do these fit? Do they replace the plastic windscreen screws?

That is a place they would fit. M4, M5, and M6 are the most common bolts on Japanese bikes. I like to have a small pile of everything laying around. Cars, bikes, weird things laying around the house, all could potentially need an M5 at some point.  
I ordered an assortment of goodies. Just over a 1,000 SS nuts, bolts, washers, etc. All for ~$85