OS 9.2 is not free; no Mac OS has ever been free and no legal download sources exist.
You can try contacting Apple by phone and asking if they will sell you a replacement System disc for that specific PowerBook. If you are successful in communicating what you need, all you will require is the PowerBook's serial number and a credit card. The cost is not unreasonable - $20 or so.
Depending on the exact model number PowerBook G3, you may also be able to install a version of OS X up to and including Jaguar. Aftermarket sources exist; search your favourite software vendor. Apple no longer sells it.
Alternately you can try some of the links listed at this site. Sometimes a reasonable priced item is to be found.
Other possible sources
http://www.amazon.com/s/?ie=UTF8&keywords=mac+os+9&tag=googhydr-20&index=aps&hva did=4031181581&hvpos=1t1&hvexid=&hvnetw=s&hvrand=1598211647358243284&hvpone=&hvp two=&hvqmt=b&hvdev=c&ref=pd_sl_540ce5fufg_b