I just found some GBA rom sites while looking for a specific rom for someone on this forum. (Sorry, no luck for that rom. )
I have found these two sites though. I'm sorry if they have already been posted and I just wasted your time.
Here they are.
http://members.xoom.virgilio.it/vesepax/roms/
and
http://www.freewebs.com/lunarblue/roms.htm
I did d/l a couple of roms off each and they all worked.