No. I needed PCIE 1x, and even for 1x versions, the bracket on the bottom is interfering with the GPU.
It needs to be some sort of flexible ribbon cable at the 1x socket, and not stick out much beyond the socket.
I think I have about 3-5mm of space
Then I don't know if what you want exists. I don't think I've ever seen a riser that can fit with <0.5 cm of clearance above the slot. The male PCIe connector itself typically sticks out further than that, let alone whatever is attached to it (i.e. ribbon cable).