Some players that have recently been released / made available that could fit the bill of what we need and are realistic targets:
Scott Cuthbert of Luton - Powerful centre half
Steve Davies of Rochdale - Big strong centre forward who can finish
Anthony Wordsworth of Southend - Talented ball playing centre midfielder
Jermaine McGlashan of Southend - Pacy winger (not sure if bit past it now)
Byron Moore of Bristol Rovers - Pacy winger
Lee Brown of Southend - Solid left back
Zeli Ismael of Bury - Useful winger
Florent Cuvelier of Walsall - Useful centre midfielder
George Glendon of Fleetwood - Tricky midfielder
Wes Thomas of Oxford - Clinical striker would be excellent in league 2
Kai Naismith of Portsmouth - Quick and direct wide forward
Will Aimson of Blackpool - Useful centre back
George Francomb of Wimbledon - good wide player
And then there is a bunch of talented players available from Boro that we could try to tempt to cross the Nene: Jack Baldwin, Anthony Grant, Chris Forrester, Junior Morias, Michael Doughty, Jermaine Anderson.
Don't be surprised to see at least one of these names pop of at the Cobblers!
I think there is a reason they are released from these clubs. I would set the bar higher!