The 67-year-old Italian has not engendered a major revival in Fulham's fortunes since he replaced the sacked Slavisa Jokanovic in November.
The London club lie second from bottom, four points adrift of safety, despite having spent more than £100 million ($127 million) in the close season.
Chelsea's veteran former England central defender Gary Cahill has been mentioned as a potential new arrival.
The 33-year-old - who has made only seven appearances this season with just one of those in the Premier League -- would provide the leadership Ranieri desires as well as vital experience for the division's leakiest defence.
"I think we have to sign somebody to survive," said Ranieri. "We have a very good team, but without experience.
"We need somebody who has experience, a leader, with good character, that's his personality, then we can improve our team.
"I need somebody who can help us; I need somebody."
Ranieri, who guided Leicester to their remarkable Premier League title win in 2016 before being fired a few months into the following season, faces a potentially crucial relegation showdown with fifth-from-bottom Burnley on Saturday.
He is not concerned that the players' morale has been dented going into the match despite the shock defeat by fourth-tier Oldham in the FA Cup last weekend.
"I'm positive because I believe in this team and this club," said Ranieri. "But also Burnley think, 'if we kill Fulham we go up'.
"And for this reason, I think it's a very, very crucial match. Believe me, at the moment I never look at the table.
"Because I know where we are, staying under water and I want to go up."