What you need is:
1X Sentria II outer bag
1X Heritage II/Legend/Legend II mini emptor
1X Heritage II thru G5 fill tube
1X G5 elbow
4X Long zip ties (2X for each end of the fill tube
A note about the last item on the list, the elbow: Any elbow designed to be screwed into the Heritage II thru G5 fill tube will work, however the G5 elbow is the one I recommend. For one, it grips the fill tube better. For two, it grips the disposable bag better. Forr three, it has the loop and fork at the top enabling it to be suspended and supported inside the Sentria II outer bag.
With this setup, you can use genuine Kirby HEPA disposable bags. The cardboard collars on these have the means to fit to both the F Type elbow, like the Sentria II uses, and the previous twist type elbow, like you would be installing in your setup. Regardless of the elbow you choose, you’ll actually be using the exact same HEPA disposable bag.
Hope this clears things up.