As Lewis' family, friends and colleagues prepare for his funeral, the Fraternal Order of Police and Illinois Department of Corrections added to the growing reward Wednesday.
Police made another appeal in the neighborhood where Lewis lived and died.
"If you have any information, please call the numbers that are listed there," one police officer told a resident.
"I hope like heck you all find these people because if they don't have no bones about killing a police officer, what the heck do they think about us?" said James Ruffin, Austin neighborhood resident.
At the store where Lewis was gunned down by two masked men a sign now orders customers to show their face. Officers have been coming to the store all week in a pilgrimage of respect. A donation box now sits at the counter where Lewis stood guard.
"Walking in here today and not seeing him standing right here with his newspaper and his smile is just really, really weird. It just shows you that tomorrow is not promised," said Danisha Simmons, customer.
Investigators have received numerous tips from the public, but none has cracked the case.
Though the store has multiple surveillance cameras, police have not released a picture of the suspects.
"They're decent photographs, but the actual descriptions of what you might be looking at may not help us at this point, so we're going to hold off on that," said Supt. Garry McCarthy, Chicago Police Department.
It is believed one of the guns used against Lewis was a TEC9 semi-automatic pistol similar. Though it hasn't been recovered, on Wednesday police displayed some of the more than 130 illegal guns confiscated by officers on New Year's Eve alone. Those illegal weapons, police say, are a direct threat to officers.
"I want to encourage anyone who is harboring illegal weapons in their homes to turn those guns in," said Ald. Deborah Graham, 29th Ward.
On Thursday, Lewis' loved ones will gather at his fiancee's church, United Baptist on West Roosevelt. His large police family, including his partner and sergeant, are expected to be there.
"The most important thing is just to be strong, for each other, gotta stick together, gotta be strong for Clifton's family," said Sgt. Wilfredo Roman, Lewis' supervisor.
"He loved his daughter. He loved his stepson, loved his fiancée. He loved this department, loved this team," said Officer Calvin Jones, Lewis' partner.
There is a public viewing at the church at 10 a.m. Thursday. Lewis' co-workers at the store say they plan to be there. They say Lewis was a regular customer and a friend long before he started working there last month. Colleagues say that job was one of three jobs that he had. He also worked security at another store.