I simply use some spare computer speakers. As a matter of fact, I use 3 sets. I like to use these because I am constantly changing the volume and having a volume knob on them makes it easy. It prevents wear and tear on the scanner volume knob, which for the 396xt is not very friendly.
Any Amplified speaker such as computer speakers should work on the BCD-436HP or any other scanner,you dont have to get Bose,but a decent set should do the trick,since most computer speakers come with a 3.5mm plug on the end.