I made this one from listening to gmendoza & the incubator has been amazing !! Temps stay steady, no regulating at all except once. The humidity also stays put based on how much water I keep in the plastic school box under the fan.
Since I already had aquariums, all I needed was the fan. Just pulled in my 15 gallon aquarium ... going to make another one for the new set of eggs & all I need is a $6 walmart fan. If you have to buy new, you can get most supplies from Walmart.
The only thing I want to add to this set up is a hose with a funnel. That will keep me from having to lift off the Plexiglas. (gmendoza uses glass; it's all I had on hand).