Wing nuts?
The factory used acorn nuts on the 2 bolt covers. Is that what you are refering to?
Any decent hardware store should have them, but since you live in the land of Metric, you could mail order them from McMaster-Carr or Fastenal. Should be 3/8-24 if I remember correctly...
If you are talking about a 4 bolt cover, then perhaps these would work?
http://store.summitracing.com/partdetail.asp?part=SUM%2DG3420%2D4&autoview=sku
