Charity Crimestoppers appealed for anonymous information following the discovery of the body of the 53-year-old man in Akholt Wood, near Aylesham, on Tuesday April 27.
Detectives said they still had no motive or suspect for Ms James’ murder more than a week after it happened.
It comes as Kent Force expands its search for the investigation.
Kent and Essex Serious Crime Branch detectives arranged for Aylesham officers to expand their search in surrounding areas after Mrs. James was found dead just before 4 p.m. on the day in question.
Officers now plan to search a number of other locations in addition to the initial crime scene in and around the woods.
They also remain keen to hear from anyone who was in the area outlined by the red lines on the map below between 1 p.m. and 4:30 p.m. on April 27.
The area is bounded by the trails of Spinney Lane to the north, Aylesham Road to the east, Holt Street to the south and Pond Lane to the west.
Mick Duthie of the charity said: “Crimestoppers are here to help people who – for whatever reason – don’t want or can’t speak directly to the police, but want to do the right thing.
“By contacting our charity with information, we guarantee that you will remain 100% anonymous.
“We are not interested in who you are and we will never ask you for your details – all we want is information, no matter how small, that could help find those behind this murder.
“Julia’s life has been mercilessly taken. If you know who was involved, remember our charity’s unique service ensuring that your anonymity is there for you.
Wednesday, police released a picture of Ms James in the same clothes she wore before she was found dead.
The image shows Ms James walking her dog Toby while wearing a light blue waterproof coat, blue jeans and dark brown Wellington-style boots.
Police said the clothes, except for the gloves, were the same as those worn by Ms James when her body was discovered.
Police said they hoped the image “would spark a memory” in anyone who saw it.
Ms James was working at home the day she was killed, before taking a walk.
Her body was found around 4 p.m. by members of the public and an autopsy confirmed that she died of serious head injuries.
Deputy Chief Constable Tom Richards said Julia’s dog, which was found at the scene, was part of the forensic strategy, but would not go into details.
A total of 449 vehicles were stopped in the area on Tuesday – a week after the murder – as officers attempted to glean new information from potential witnesses.