So far, I've found four of the five children marrying in Bothwell. A brother, Alexander, died in Jan 1934 and James registered the death giving his address as 181 Main Street, Uddingston.
I did wonder if one of his children emigrated and he'd gone abroad with them but I haven't been able to trace evidence. One son definitely died in Coatbridge in 1960 so there were still relatives living in the area well into James' dotage if he survived that long.
Several others have been searching for James' death for quite some time without success so it's proving a real mystery. In a way, trying to find a headstone online was my big hope.