Here is a link to avian classifieds - you may want to post your question there:
index.php
And here is one more - Birds'n Ways Classifieds:
http://www.birdsnways.com/birds/bpreown.htm
Other than that, I don't really know... We are mostly pet owners here but hopefully someone else has more ideas.
I had a bird shipped from the East Coast to West Coast. If you pay by cheque, you will have a proof of payment. But it's definitely more risky than buying something in person. I would say that if you buy the birds from a reputable breeder (ask for references), you should be fine... I was definitely more worried about Jamie's trip accross Canada than I was about my payment! lol
Kate