I found this guy. https://www.jesent.co.uk/product-page/window-box-dark-brown-with-a-difference-standard-brackets-box-free-p-p In the end it is a C-clamp that needs A rubberized grip on both sides. All of the home depot ones look like they would actually damage a window Ssill. They got the reject monitor desk mount c-clamps. Looking through Alibaba. Otherwise, I might buy the Brits but $25 for a set seems steep though I don't know the cost of things anymore.