Hi webbyboy, welcome to Simviation!
The most probable solution is that you don't need one! Radio beams are narrow at source but widen at distance, and the air is a fluid medium; so any aeroplane will take its time lining up, particularly when it's a long way out (like 15 miles). If you look at the first few screenshots in the tute, you'll see that my 737 was by no means completely lined up at first. So first of all be patient, let the aeroplane get closer, and you'll probably find that it lines up perfectly closer in when the beam has narrowed down.
If that doesn't solve the problem, chances are that you're getting one or other of the settings wrong - too much flap, not enough power, not enough speed, or whatever - and the aeroplane is 'toppling' because it is getting close to stalling speed. Whichever aircraft you're flying, look it up in the Learning Centre Index (under its name, e.g. 'Boeing 737' is under 'B'), read the Flight Notes, and make sure that you are getting all the settings right.
If none of that works, glad to help further - but please say which aeroplane you're flying, whether there's any wind, what approach speeds and flap settings you're using, etc.; it'll make a 'diagnosis' easier.