The Standard Liege defender flew into Glasgow for talks with Celtic on Friday and agent Dudu Dahan today claimed his transfer had been agreed subject to work permit issues.
Dahan posted a picture of his client signing a contract at Celtic Park on his Scoutpush company's Facebook page and it appears only a visa is needed to conclude the transfer.
Dahan said a six-month loan deal had been agreed with the further option of a three-year contract.
The agent added that Gershon would travel to Belgium to sort his work papers and would then join Celtic in Spain, where they will travel later this week.
The 24-year-old spent much of last year on loan to Liege's Belgian top-tier rivals Kortrijk.
He could help fill the void left by Efe Ambrose while the Nigeria defender is on African Nations Cup duty.