The 34-year-old former Hull City custodian comes in from Bradford City and could make an immediate debut against Macclesfield on Tuesday night.
Aidy Boothroyd moved quickly to snap up Duke after losing Chris Weale to injury with goalkeeping coach Tim Flowers giving a thumbs-up to a player he has worked with before.
"I think he's exactly what we need," Boothroyd told the official NTFC website.