HDMI Dummy Plug : ID 4247 : $3.50 : Adafruit Industries, Unique & fun DIY electronics and kits
HDMI Dummy Plug 4K High Resolution Virtual Monitor Display Emulator New Generation Headless Display Adapter Compatible with Windows Mac OSX Linux, 3Pack - Newegg.com
dtech T0667-5 DTEcH 4K HDMI Dummy Plug Display Emulator Headless ghost Adapter compatible with Windows Mac OSX Linux Support 4kx2k 2160P 1080p