"Mido is clearly the new Juninho with our fans. Shirts beating his name are in very heavy demand," a Boro spokesman said on the club's official website.
"The Premier League has changed the number design this season and, because we don't compromise on quality, we are asking fans to be patient until the new stock arrives."
After an urgent order has gone in to the Premier League's official suppliers, the new stock of numbers is expected to be available within the next week, Middlesbrough said.
Mido has become a hero at Riverside even though he has arrived just a month ago from Tottenham Hotspur.
He made an instant impact with Gareth Southgate's men, netting two goals in two successive Premiership games.
Middlesbrough's reputation in Egypt has further increased following the arrival of Mido's fellow countryman Mohamed Shawky from Egyptian champions Ahli.
"In August alone, more than 41,000 Egyptians visited Boro's website, compared to just 240 12 months earlier," the club said.