I've used https://github.com/abdmob/x2js in NetSuite without issue

Were you able to make this work serverside? Tried it once, was not able to make it work

Yes, something like this

define(['path/to/x2js'], function(X2JS) {
  ...
  var x2js = new X2JS();
  var xmlstring = x2js.json2xml_str(js object);
});