I wonder how useful they are. I used to have a gaming laptop in the early 2010s and the nicest cooling fan I could find, but it only dropped the temperature down by 2-3 degrees
My suspicion is that they're not useful at all. Once I bought such a cooler pad, and placed a 2011 13" MacBook on it. Then I benchmarked it (i.e. max out the CPU), and measured the sensor "CPU Near". I could not measure a difference between the cooler pad on or off.
I can't remember the brand of the cooler pad, but it had two 10 cm fans.