Looking for Roofing Screws (see pics)

[Mindy Jensen]

Does anyone know where I can purchase a roofing screw like this? The bonded washer needs to be very wide like in this photo. I’ve tried all the building stores in town, no luck (they have ones w less-wide washers but I need x-wide for polycarbonate sheets, which will expand when warm, for a greenhouse I’m building). A google search isn’t much help, either...even just ideas on search terms would help me! I’ve used “roofing screw, bonded washer, extra wide”...but just come up w standard ones like I find locally. What else might I search?)