Well, if this were my project, I'd take a look for surplus high-current
AC tabletop supplies (transformers). I see that Jameco has a 13.5Vac 5
amp table-top supply for $16.95. That's 67.5 W, if my math is correct.
Since the 9VAC is used sparingly in the C64, a couple of 4 volt zeners
ought to take care of that part. As far as the 5V supply, a simple
rectifier+filter and buck regulator ought to get me there. The supply
is already UL/CSA approved, so no issue there.
But that's just me.
--Chuck