Ebay is probably the best bet, though the thing is to be patient. It is kind of like sitting beside a stream, watching fish drift by. Eventually, a slow, big fish will probably come within reach... and reasonable price is a variable dependent on your personal threshold. How long you wait really depends on how much you want to spend, but given that there were literaly thousands of these toys produced, the odds are in your favor. Trouble with eBay is that folks get impatient and buy overpriced items, driving up the selling history values & raising sellers' expectations into the 'stoopid' range.
Since the Falcons are no longer in production & sold out in stores, there is most likely no "normal" channel to get one. This means that there are folks looking to make a buck off ones they have. Then there will be those who are 'yard sale' sellers disposing of old kid's toys so the quality will vary. With luck, you can get a fairly clean and complete copy locally (like I did with my Hasbro Slave 1...)
R/ Robert