I'm on mobile so can't easily pull up an example part number, but digital signage controllers can often be PoE powered. They're insanely overpriced new from the actual suppliers, but for hobby projects they can normally be sourced relatively easily on ebay. The trick is that many of the ebay sellers don't bother listing the specs, so you need to first search digital sign cintroller/computer on ebay then look up the spec sheet from the model number.