You can buy the individual pieces here
http://www.hondaautomotiveparts.com/...NTENNA-SPEAKER
I assume that you already have part 8 since someone already put rear speakers in (and I assume that you just need the covers - part 9)
There is not much room behind the speakers (especially on the passenger side) and the hole cut-out area is metal. The best thing to do would be to remove the speakers and take a look inside yourself so you can judge how much room you have for mods.
JoeCVT - Just your average CVT owner