Imperial Star Destroyer Turbolasers - supplemental sets?

I am not sure of the scale needed, but I saw the actual filming model of the ISD at the Museum of science and Industry a few years ago.  The turbo laser batteries were the gun turrets of the P-61 or the 4-gun turret of the B-29 without the aerodynamic cover, just the guns.  The filming model used them in 1/72 scale.  That could be a source that would not involve expensive aftermarket kits.  Hope this helps.

Like these?

Or like this?

The turret in the second picture looks like it came from the mantlet of a Panzer I or Panzer II tank, which wouldn't be too surprising given the original models were basically kit based from a variety of kits from the time. 

Like none of the above.  The arrangement was 4 guns, in 2 levels.  It literally was the part from the B-29 or P-61 4 gun turret with out the cover, probably in 1/72 scale.  I was amazed to find  piece of a model I directly recognized.  I built both the P-61 and B-29 in 1/48, but the part was the same on both models.  the top of the turret was open.  Just to be clear, I am talking about the heavy turrets on the top of the ship, on either side of the bridge structure.  I found some ok pictures on www.theforce.net/.../isd.html which show what I am talking about.  I amnot sure what they used to model the turrets on the sides of the vessel.  Hope this helps.

Do like the original prop builders did..... do your own thing, man. Those original Star Destroyer props had crap from all kinds of old model kits. Just have fun with it.