I bought some of these extra when I did an ESD mat group buy a while back. No need for them now... they are 10mm snap/stud kits, as seen
here.
$3.60 shipped for one (PayPal)
$4.60 for two
$5.60 for three.
After three each one is $1.20 extra (shipping cost increases

). Let me know if you want some!
SOLD! Turns out I only had four...