Vinyl top trim fasteners - looking for source

I used the same clips on posts with a pal nut that were used on the rest of the top back there. It's a pain getting to the backs to get a nut on the post - definitely easier with some else helping to hold the trim in place, but I think the only reason they used those odd screws is that they didn't want to take the time on the line to get someone in the trunk and someone outside to install the clips.