My evaporative cooler is made up of a few parts. The main body is made up of 3 parts.

The base is a 8" (not too sure could be 10") PVC part that converts to 6". This is to provide a stable base and to house my submersible pump.

The next part is the top with a 5/8" barb for intake. The barb looks like aluminum but the guy assured me that it was brass with a different color.

The last part is the white PVC part which is a 6" pipe with a 4" Y. This was a second-hand one which the shopkeeper sold to me cheap. The 4" Y is perfect for a 120mm fan.

The base cost me around $12 USD, top part and the Y for another $12. Total cost around $24 excluding some PVC elbows for the showerhead.

Next we look at the pump I'm using. Its a submersible 3000l/hr unit Atman product. It comes with 3/4" fittings which I was able to squeeze a 5/8" hose into. Cost me around $25 USD.

Now, we look at the reservoir I'm using.

I dont know the actual volume it can hold, but its definitely big enough for me to go running for days without refilling if I had wanted to. Got it for around USD $7.

Next is the showerhead. The one I picked was around 3" in diameter and came with quite some holes. However, I drilled many more holes so that it had hundreds of holes.

Sounds funny but I just couldn't find an appropriate sized elbow to screw it into so I had to burn the perimeter of the elbow and stuff the shower head in. I had also removed the flow restrictor in it. I then used silicone on the perimeter to seal it.

Next, putting them together...