Where do I find the push fasteners for sail panels?

'72 Swinger, sail panels... each is held to the body by two nylon push fasteners. The fastener has a "two-step" head, and the upper part has a notch so it can be rotated into the panel boss and retain it.
A look on ebay showed over 9,000 entries for plastic push fasteners! Can someone please tell me what the correct name is for these pins, and where to get them?
thanks :)