Not happy with my air assist.
Mine makes too much noise and doesn’t work well.
I have seen where Air Brush Compressors have been
used and they have a water separator for dry air (no oil)
and adjustable PSI regulator.
I just don’t know how the hose terminates. It looks
like a proprietary screw on fitting for air brushes, but
how do you adapt that to a 5mm - 8mm hose ?
This may help you: http://sumidacrossing.org/Tools/Airbrush/AirbrushHoses/ConnectorStandards/ but your best bet may be to connect an airbrush hose to the compressor and cut off the fitting at the other(laser) end.
I have a K40 and I just added air assist with this compressor from Harbor Freight http://t.harborfreight.com/16-hp-58-psi-oilless-airbrush-compressor-60329.html . I have the LightObjects air assist head. I used the hose that came with the compressor and just cut the end off. It fits the LO head but it’s tight. All seems to work great, nice and quite. The compressor dose get warm.
@FNG_Services Is the compressor quiet? I have an airbrush compressor but it’s the loudest piece of equipment in the room.
That’s the compressor I’m looking at, but
I want quiet. The air pump I have is too
loud,the buzzing drives me nuts and it’s
even sitting on the basement floor.
It’s very quiet, I have it setting right up next to my laser and the fan on the power supply of the laser is loader then the compressor. With both the power supply fan and the exhaust fan running you will never here the compressor. There are a couple of videos out on YouTube that show how quiet it is.
My solution to noisy stuff is to just crank the music louder haha. But I am using an air-pump from a tanning airbrush kit I got for my air-assist. It is about as loud as an aquarium air-pump. I literally just zip-tied it to the laser head (just as a test to see if it works well enough to actually use permanently).
They all make noise, unless you have a low-power one with an acoustic baffle chamber but they don’t have the power.
For power and silence you want a magnetic air pump, pricier but cool and high-tech 
And for sizing, cut off the end of the tube and use an aquarium inline adapter.
I received my Harbor Freight 1/5HP 58PSI
air brush compressor today and this thing
is quiet ! I paid $80.00 w/coupon + S/H.
It came with an air brush set, but I’ll give
that away to someone that can use it.
Mine should arrive tomorrow.
Found the same on in the UK :
During the last few days I did some light etching in hobby plywood and this pump
gets Hot To The Touch in a short time. I
kept on going for a few hours and the pump
kept going, just hot !