There are native bluetooth third-party keyboards, like the Logitech diNovo media desktop. But that one is definitely more expensive than the Apple $70 keyboard, because AFAIK it can't be purchased as "keyboard only", but you need to get the entire kit (bluetooth receiver, keyboard, mediapad and mouse). And I don't know if it will work on a Powerbook.
I recommend that you get the Apple keyboard, especially for compatibility reasons. You don't want a keyboard where you don't have the Alt or Option key, or where it doesn't work as expected. I have the Apple one and didn't regret the purchase - even if the keys could be better.
|Quoting Cba (Thread starter):|
why are bluetooth wireless devices almost barely available?
Unfortunately I'm unable to answer that one.