how and where can I get OS X 10.4.7 disc 2

I no the discs that come with the computer are made just for this computer so how do I go about getting a replacement for a lost disc? can I down load it and copy it to disc or do I have to have it send to me? I already started the instalation process with disc one and thought I had disc 2 but couldn' find it.

thanks for your help