M-D Frame Clip for Screen Frame, White Plastic, 1-in x 5/16-in, Temperature Resistant, Screws Included in the Screen Frame Connectors department at Lowes.com
Clip or Sign Frames. Black Poster Holder, A4 size. Sign Frames Shipped Australia Wide
Amazon.com - MCS Clip Frame 16 in. x 20 in. - Art Framing Supplies
Amazon.com: Quadro Clip Frame 16x20 inch Borderless Frame, Box of 2 : Home & Kitchen