This handy tip from Reddit user afhn_ reveals how you can avoid your laptop from heating up when you can't find a cooling pad. The trick is to prop your laptop on four
plastic bottle caps such as those found on 20oz soda bottles to increase the airflow underneath the device.
Of course, it probably works best if you don't intend to actually move the laptop around. Purchasing a commercial cooling pad is still the best option since it will offer more stability, especially if you intend to do a lot of typing.