The trick to a shaft of light isn't the instrument. You can create a nice shaft of light with just about any instrument that will focus a fairly hard edge. The trick is that the light needs tiny particles floating in the air to hit in order to be visible as a shaft of light. So that means you need a little bit of fog or preferably a hazer to give that air something for the shaft of light to illuminate. Rent a hazer, grab an ellipsoidal or two and throw in some orange gel... nothing too expensive there.
Toss an iris in any ellipsoidal and you can get the size you need. Like gafftaper said, create some kind of atmosphere and the shaft of light will really stand out. I had a client that wanted a light coming down from the catwalk to be God. I ran a hose out of a coldflow unit and gaff taped it to a 10 degree Source 4 and the smoke "fell from heaven."