The phrase "was a regular visitor" is correct and usable in written English.
You can use it to mean that someone visited often. Example: My grandma was a regular visitor to our house when I was a child.
Mr Iyengar was a regular visitor.
The affidavits indicate Anderson was a regular visitor to Balco.
In his life after baseball, Thomson was a regular visitor to charity events.
Felix, who used to flog Oz magazine on the King's Road, was a regular visitor.
Savile was a regular visitor to Jersey but denied ever visiting the home.
Indira Gandhi was a regular visitor to his ashrams through India, he said.
Back then, Mr. Barrant said, he was a regular visitor to the school's offices.
Smith was a regular visitor at the juvenile courts and police stations of Sydney.
Naiyyar's daughter-in-law, Qaisar Khan, said he was a regular visitor to Karachi.
Mrs. Roosevelt was a regular visitor when she was in Hyde Park.
He was a regular visitor over the years, very plausible and charming and ingratiated himself.
