The best place to find speakers at an affordable price would be Amazon.com. You can buy used or new, and you have available thousands of products to choose from. Also, customer reviews are available as well.
It doesn't need a speaker.
So you can hear sound from the computer.
Yes you can definitely use a computer speaker even if your built in speaker broke. Local electronic stores and major retailers such as Myer sell computer accessories. You could visit your local computer store that sells computer speakers too.
Just like any other speaker.
There are several places to buy computer speakers from online. Some common sites for this equipment are www.bestbuy.com, www.amazon.com, and www.newegg.com
I activating my speaker.
It's usually a small speaker mounted to your computer case. Some mother boards will have it soldered directly to the board.
A speaker would be considered a communication device.
There are lots of computer speaker brands available in the market. One has to be careful when selecting and purchasing one. As a guide, I will recommend you check www.digitaltrends.com/.
Wires And A Amplifiers
No.....!
a wearable computer