Something like that was a real problem some time ago but should not anymore.
Maybe these two threads contain info on how to fix this.
or maybe even in this forum - I did not search here.
Copying what is missing (wget) off of the live-CD might work too.
If your Browser is still functional or you got links or lynx installed, or some ftp client - then the downloading is still possible - if getting the source is the only thing which prevents you from rebuilding.
The downloaded source-files normally go into /usr/portage/distfiles (or to the $DISTDIR defined in /etc/make.conf if you have changed the default)