I don’t have a commercial brooder. I use a large plastic tub with aspen chips in the bottom and a heating pad underneath. I have a thermostat on the side to keep track of the temp. I rarely shop at Walmart but they sell a small heating pad that keeps the temps in the upper 90’s and doesn’t automatically shut off like some others. I’ve found them perfect for keeping the temps right where I need them. I even use them when I move babies out of the brooder into a cage. I put it under a corner just to give a warm spot and I keep the cage covered from drafts.
This has worked well for me. I keep two large tubs. One on standby with fresh aspen in it so I can change it each day. It’s important to make sure everything is kept clean and if you use aspen make sure you check it for sharp pieces before you put the birds in it.
Ive heard of people using bread proofing boxes as brooders and incubators but I’ve never done it myself.