Vauxhall Corsa Stereo Plus Back Board? HELP!?

[x_PrivateCaller_x]

I have a Vauxhall Corsa and I am after a new stereo. However, after speaking to my friend, he says that I am in need of a back board so there is not a big gap where the manufactured stereo was (As we all know, the built in stereos are HUGE!) Does anybody know where I can pick one of these up from? And how much?

Thank you Guys!