The prince once was the target of Milligan's jokes when the comedian called Charles "grovelling" in a live TV interview, Hellomagazine.com said.
Milligan reportedly sent Charles a fax after the remark, saying, "I suppose a knighthood is out of the question now?"
A few years later, Charles knighted Milligan at St. James' Palace.
When Milligan died two years ago from suspected liver failure, Charles was among the first to pay tribute.
"Personally, but along with so many others, I shall miss his irreverent and hysterical presence and can only say that the world really will be the poorer for his departure," Charles said at the time.
The life-sized bronze sculpture reportedly will be placed in Finchley, the London area where Milligan lived.