gistfile1.js

// 1. Save gist as fixsvpplylinks.js
// 2. Install node.js (http://nodejs.org/)
// 3. 'npm install async request'
// 4. 'node fixsvpplylinks.js /path/to/wants.json'
// 5. Wait.
// 6. Don't worry about those EventEmitter warnings!
// 7. Done.

// 8. If there's any issues then give me a tweet (@artcommacode)

var fs = require('fs')
  , url = require('url')
  , async = require('async')
  , request = require('request');

if (!process.argv[2]) return console.log('You must provide an input file');

fs.readFile(process.argv[2], 'utf8', function readFile (error, body) {
  if (error) return console.log(error);
  body = body.split('][').join(',');
  try {
    body = JSON.parse(body);
  } catch (e) {
    return console.log(e);
  }
  async.map(body, function parseItem (item, callback) {
    request(item.page_url, function retrievedURL (error, response, body) {
      if (error) return callback(error);
      item.page_url = url.parse(response.request.uri.href, true).query.redirect;
      callback(null, item);
    });
  }, function parsedItems (error, items) {
    if (error) return console.log(error);
    var newFile = process.argv[2].split('.json').join('.parsed.json');
    fs.writeFile(newFile, JSON.stringify(items), function wroteFile (error) {
      if (error) return console.log(error);
      return console.log('Done: ' + newFile);
    });
  });
});

My export file contained a null element at the end of the body, so weird.

Just added a quick check that the item is defined at L27:

if(!item) return;