Osimhen is on a season-long loan with Galatasaray, with his contract now carrying a buyout clause of €81m, which will drop to €75m next summer.
Fanatik says United are in talks with Napoli about a cash-plus-player exchange for the Nigeria international.
United are prepared to send Josh Zirkzee to Napoli plus a couple of million euros in exchange for Osimhen.
And it's an offer that Napoli is seriously considering, with coach Antonio Conte already approving the deal.