The Northants Marriage Index does not show the marriages of Wright or James/Elizabeth under the spelling Fitzjohn, however this looks like Wright ...
Wright Fidgeon = Ruth Royal 1751 Apr 9 Kings Cliffe
... and another variant from Ancestry ...
James Fidgen = Elizabeth Wright 1766 Mar 31 Liddington, Rutland
These appear to be children of Wright on the Northants Baptism Index ...
Wright s/o Wright bpt 1754 Mar 15 Kings Cliffe CofE
John s/o Wright bpt 1758 Jul 16 Kings Cliffe CofE
Thomas s/o Wright bpt 1761 Jan 18 Kings Cliffe CofE
James s/o Wright bpt 1764 Mar 13 Kings Cliffe CofE
William s/o Wright bpt 17657 Apr 5 Kings Cliffe CofE
Ruth d/o Wright & Ruth bpt 1771 Jan 6 Kings Cliffe CofE
Ruth wife of Wright died 1795 [Northants Burial Index]
There's also info on Wright's family on FamilySearch at ...
https://www.familysearch.org/search/record/results?count=20&query=%2Bgivenname%3AWright~%20%2Bsurname%3AFitzjohn~%20%2Bmarriage_year%3A1740-1760~These appear to be children of James on the Northants Baptism Index ...
?Ann d/o James bpt 1766 Nov 30 Kings Cliffe CofE?
James s/o James & Elizabeth bpt 1769 Mar 17 Kings Cliffe CofE
Susanna d/o James & Elizabeth bpt 1771 Feb 10 Kings Cliffe CofE
Elizabeth d/o James & Elizabeth bpt 1773 Jan 6 Kings Cliffe CofE
Sarah d/o James & Elizabeth bpt 1775 Jan 14 Kings Cliffe CofE
Jane d/o James & Elizabeth bpt 1777 Mar 16 Kings Cliffe CofE
Thomas s/o James & Elizabeth bpt 1779 Mar 14 Kings Cliffe CofE
Lucy d/o James & Elizabeth bpt 1782 Jan 3 Kings Cliffe CofE
I wonder if the later info that I assume you already have will lead you towards which one is the father of your James.