Other option would be using a tree-grid-view. But I also would be happy about a ReverseItemsGrid.html variant in Innovator 12. It has a few pros and cons but it´s often easier to use and faster.
From my POV most of the original code should still work in I12. I would ask Aras if they still can offer a I12 version for this one.
As alternative you can use the browser debugger to step through the code and look for the outdated code. Right now I would add the following line for the QueryItem function to work:
<script type="text/javascript" src="../../../javascript/QueryString.js"></script>
(Not tested, I just had to use it in my own variant)