based on https://www.thingiverse.com/thing:1908624, but with thicker walls so a scaled version can be printed.
i redid the model based on rocket nozzle in open scad, i did it with a solid upper ignition block and thicker walls. nozzle is open at bottom but appears bigger than it is, it is for easier printing. also it is scaled to 0.16 of rocket model. so if you want it to be as big, scale it up by 6.25x