Walker was released by National League side Barrow AFC at the end of last season.
Walker netted the winner in Barrow’s Wembley win of 2010 and scored 91 goals in 254 appearances for the club over two spells from 2007 to 2011 and between 2014 and the 2015/16 season.
Formerly with Dundee and Greenock Morton, the 32-year-old originally joined the Bluebirds from Morecambe.
He returned following spells with Luton Town, York City and Forest Green Rovers.