You are in luck, I still have the bag they came in.
PN A 202 992 00 10 -- mine is a 1997.
They are little dark green donuts (although the color probably doesn't matter) and just under 3/4" diameter. They have two ribs running around the outer radius, creating a center channel. After forcing it into the metal hole, the channel is what keeps it in place.
I got them from Brian at Europac West 877-996-9499.
Happy to help.