Just checking on Transfermarkt and what they list as players without clubs, couple of names I think would slide in nicely to the squad:
Ryan Tunnicliffe - Central Mid - 31 appearances for Milwall last season, comes from the Man United youth setup. Could slot in nicely next to Henry or play a bit wider if needed
Chris Long - Centre Forward - 30 appearance for Fleetwood last season, only 3 goals, but I recall him being floated around this time last year
Greg Stewart - Centre Forward - 36 appearances for Aberdeen (on loan from Birmingham), with 10 goals and 10 assists. Perhaps one of the players we were looking at up North recently.