I had to build my own, on the "heating and air conditioning" section there is post on the recent dual stage swampcooler I been testing. It has been working great, if i build anymore they will be dual stage, the performance is noticeable compared to just a regular swampcooler. I never seen anyone sell the dual stage swampcoolers, so you have to build it yourself. I been using swampcoolers for 9 years and they make a big difference in keeping you cool, having max insulation allows you to stay cool with minimal power use.I've been thinking about trying out some kind of a swamp cooler or making one. Would you mind sharing what kind you have and where you got it.
As far as insulation I used regular 1/2 inch generic gluesticks (cheapest ones) to install the insulation to my bare metal roof, I installed the first layers in 2013, 9 years later they are still on the roof, never fallen off. I use hotglue because it has no fumes and it dries within minutes. You can hotglue foam on top of other foam, making multiple layers.
roof insulation 6 layers (1/2 inch per layer) . With 6 layers I no longer felt any heat coming in through the roof.