I got mine off Amazon, but also lots available on ebay. Just search for “HDMI LCD Controller Board” there are lots of different options. I found one that just had the single hdmi output instead of multiple outputs to save space.
You may need to email some of the sellers to check the board is compatible with your LCD panel. If it’s not they may suggest a similar one.
Best option is to look at the part number on the back of the LCD panel, my screen was out of a Sony Vaio laptop but was a Hitachi LCD panel, I searched for "HDMI LCD Controller Board + ‘LCD part number’ " and that came up with a couple of results, make sure the resolution is correct as well.