Blades manager Chris Wilder is seeking to add firepower to lead their safety bid.
The Blades lie well adrift at the bottom of the Premier League table, 11 points behind Burnley in 17th having taken just two points from their first 15 games.
And with just eight goals scored so far in the campaign, Wilder has identified Nisbet as his main target in the January window, says The Sun.
Wilder's planned overhaul next month will focus on low-cost players after big outlays since their Premier League promotion in 2019.
The 23-year-old has 12 goals in 24 appearances so far for Hibs, after joining in a £250,000 deal from Dunfermline in the summer.