Acting major Claude Llewell Harris was killed instantly as he lead his company into battle during the capture of Vimy Ridge in France in 1917.
The 24-year-old from Wakefield was serving with the Canadian Army and his mother Annie Harris, of Rishworth Street, was later given a medal to commemorate his death.
His Canada Memorial Cross is now up for sale on an internet auction site and a Canadian history enthusiast is hoping to trace his family so they can be reunited with the medal.
Dave Thomson, from Ontario, has been named Canada’s “medal detector” as he uses the web to trace war medals and get them returned to families or communities.
He has been successful nearly 600 times in the past six years, including with families in Shrewsbury and Scotland.
Mr Thomson, 54, said: “As a society we have our own ways of paying respect to our veterans and repatriating these medals to their families is mine.
“We have the opportunity to bring this medal home and in the past communities have raise dthe money to have them in their museums.”
The cross is up for sale on eBay for C$700, which is about £435, until Christmas Day.
But Mr Thomson added: “This may seem like a lot of money, but he was a high ranking officer who died in Vimy Ridge, making it valuable to collectors.
“The fact he rose through the ranks shows his leadership skills. This is a very rare item.”
Mr Harris was born in Wakefield in 1893, attended Wakefield Grammar School. His dad was Thomas Middleton Harris.
He moved to Canada in 1912 to work for the Bank of Montreal.
In 1915 he enlisted in British Columbia as a private in the 72nd Battalion and went to France with his unit.
In January 1916 he was promoted to lieutenant and attached to the 7th Battalion. He was later promoted to captain and severely wounded.
But he recovered to join his unit again as acting major, leading them to Vimy Ridge, where he was killed on April 9, 1917.
The Memorial Cross was awarded to wives and mothers of soldiers killed in action, but what happened to Mr Harris’ cross remains a mystery.