The other place has it at http://www.megalithic.co.uk/article.php?sid=10462 with an alternative name of Fridd Can Awen. The name appears with a slightly different NGR on http://web.ukonline.co.uk/heroese/Ave.Flds.Row.htm as one of the stone fields (you could find the list of stone fields, rows etc. useful).
http://website.lineone.net/~rkwilli/framefieldW1Sect2.htm has amongst the names for Hafod-y-Garreg (817-831) "Cae maen llwyd = Greystone Field" which must be the same thing.