Had you thought of making them? Ours are bolted to a standard sheep hurdle and made from a plywood top and ends with wooden struts between them. Access for the sheep from either side. We started with hinged tops, but found it easier to feed the hay in from the sides - saves dealing with catches in the wet!
They can feed half a dozen sheep at a time and be moved around to suit.
Let us know if you want more information!