Ravel Morrison has returned to parent club West Ham from Cardiff City on compassionate leave.
Brighton boss Sami Hyypia is weighing up a move for former France captain Alou Diarra.
Redknapp is currently without leading scorer Charlie Austin due to injury and saw QPR draw a blank for the fourth time in five games in Sunday's 0-0 stalemate with Watford.
That result dropped QPR down to fourth in the Championship table and they have scored the joint-lowest number of goals of the top 18 teams in the division.
With only 24 goals coming in 23 games this season, it is an issue Redknapp is keen to address when the transfer window opens this week.
"We had Charlie out and Bobby Zamora, while Andy Johnson can play half a game maximum," said Redknapp. "They are not fully fit.
"The Doncaster game on New Year's Day is important for us now and we are looking to bring in another striker in January if we can.
"In some ways we are lucky Charlie has been fit for as long as he has, otherwise we could have been without a striker for weeks.
"At least we are nearly at January now and may be able to get someone in."
Redknapp has been linked with a loan move for Tottenham youngster Harry Kane, who spent time in the Championship last season with Leicester City.