Hi,
His wife Emma died on 16 Feb 1923. According to her death record, the place of burial was "Chatham" and the date of burial was 19 Feb 1923. James' death record also just said "Chatham". I would assume they are buried together, so looking for them both in the same cemetery could narrow things down.
Try this link:
http://www.rootschat.com/links/0d3b/It looks as if the municipality controls the Maple Leaf Cemetery (which seems to be huge). Perhaps you can contact them and ask if your relatives are there. An earlier post provided a link to a site that has many photos of graves in this cemetery.
Also, the above link to the Chatham/Kent cemetery page has a PDF list of privately owned cemeteries in the area. Contact information is provided. See the "other cemeteries" option on the left of the page.
You know the death dates for James and Emma. Have you tried looking for an obituary in a local paper? Sometimes they say where a person is buried.
RK