I liked WayofWood's Air Assist and I wanted to modify it to fit a fan that I ripped out of an old broken laptop. I used the original nozzle but I made the back a little bit wider and added some air channels between the fan and the laser post. My laser was firing a little high so I added some support arms and a spacer to raise the x-gantry to the right height. I made a version without these arms in case your laser's x-gantry was at the right height to begin with. I ended up using a different air assist (also on my account) so this is basically untested. I thought I would put it on Thingiverse just in case someone else wanted to use it.
I used tree supports but I think normal supports will work as well.