Where to buy transformers?

I'm thinking of building my own power supply, and I need to find a
transformer for a reasonable price. While there's been a lot of posts
on the list that discuss transformer types and/or sizes, I couldn't
find any links to places that actually -sell- them at reasonable
prices. The standard online electronics houses (e.g. mouser &
digi-key) don't seem to carry large power transformers. I'm looking
for something in the 500VA - 1000VA range. Toroidal would be nice, but
I may go with the "normal" kind for price reasons.

As to size... I just purchased 3 DC motors that run at 40V nominal,
60V max, with a peak current draw of 14A/each. The guy I bought them
from recommended that I run them at 48V for CNC use. I know that I
won't ever run all three at peak current, but would a 10A (500VA)
transformer actually be sufficient, or should I shell out the $$$ for
a 20A unit?

Also, I've seen several posts that say I should multiply the AC
voltage by 1.41 to get the DC rectified voltage. In my electronics
books, however, it says that most AC voltages (such as the 110V
household voltage) are already specified in rms form. When I'm buying
a transformer, do I get a 48V secondary, or a 34V secondary?

Thanks!

- DeLesley Hutchins