Is within an auxiliary I can buy to hold on to the underside of my Mac PowerBook G4 cool during use?

Answer:

Look for a Chill wad or a cool pad. It will enjoy small fans and and will elvate your Mac for a while bit. They usually cost about $20, and plug into any a USB port or the wall.
There are also little stands you can buy that allow air to go past under the notebook.
Look for knees stands like these found here http://raindesigninc.com/products.html...

amazon.com or ebay might enjoy something like them for a better price.
I bought two of those block shaped rubber door stops in the hardware store. Cost $1.50.



They hold the PB up at the ultimate angle, air can circulate underneath so the follower comes on less frequently, and they run up very little space contained by the laptop bag.