The 26-year-old Janko scored 39 goals for Salzburg last season and has netted eight in 12 games during the current campaign.
He has also been on target seven times in 12 appearances for his country.
McLeish told the Birmingham Mail: "Janko is on a real hot goal scoring streak. He has a big presence. He's maybe not yet the same kind of level as Peter Crouch but he's trying to be that kind of player.
"These players like him are out there but can we get them to come to the club? That's the question."