There are two obvious choices.  First of all handihams sells a very 
affordable add on that gives you a tone as the antenna turns.  Its not my 
favorite but quite usable.  You might have a look at their web site.
I preferred a rotator sold by norms rotator service which essentially was a 
modified rotator with a control box and pointer.  You pointed the knob to 
the direction of your choice and pressed a button.  There was a tone until 
the beam got to that point.
Good luck with the tower projects.  Buying one can be easier than putting it 
up.
Richard