Hi,
Here is a link to the service manual for your laptop.
If you scroll to section 5-42. It details the procedure for the removal of the internal speakers. At the top of the section it also gives the part number for the speaker. Just Google the number (nothing else) to get results for suppliers of the part.
http://www.hp.com/ctg/Manual/c00444244.pdf
Hopefully this is of some help.