you could use Download Adobe CS4 and CS3 Free Trials – Direct Links (incl. AE) | ProDesignTools to load down a trial, which you can later change into a "real" version.
BUT read before downloading the "Note: Very Important Instructions", to get it successfully.
... and not to forget here the update-link: Adobe - Fireworks Support Center : Downloads : Updaters see:
>>> Fireworks CS4 10.0.4 updater for Mac OS X and
>>> Fireworks CS4 10.0.3 updater
My previous answer becomes moderated, so you can't see it at the moment.
I saw both of your responses, thank you for that. I was able to get through the instructions and downloaded the trial for now.
What do you mean by "... which you can later change into a "real" version."?
Also I purchased my CS4 years back through a course, but it doesn't not show up in my account. Do you know where do find serial numbers?
you should have a look at Adobe's database, to see what's stored/saved about your accounts. Here you will find general infos about your Adobe Account https://accounts.adobe.com/>>> see My productsView all >>> These registered products are associated with your Adobe ID. >>> Name >>> Serial number.
And to find your serial number have a look there http://helpx.adobe.com/x-productkb/global/find-serial-number.html >>> I lost my serial number >> see comment
The last time Adobe suggests so too this
Sorry, I couldn't answer earlier.