The 1942 version of the Buchanan is available from the ususal online store suspects. I've seen it on the Squadron and Sprue Brothers sites. Check the sites of the advertizers who support this site. I bought mine from Dragon/Cyberhobby
http://www.cyber-hobby.com/shop/
The 1945 version is a limited run kit. There were a few left over inventory from the IPMS Nats supplied to Freetime Hobbies, but they are now sold out. You may still be able to buy some from the Cyberhobby online store.
--EDIT 0855 - 23AUG08 --
Just got an email from Dragon/Cyberhobby. They are sold out of the 1945 Buchanans also.
-- END EDIT --
Online ordering from most online shops is quite easy with a credit card or paypal. Most sites have a shopping cart system which make it easy for you to spend your money. Shipping to Okinawa may add some to the cost, if you are military it may be cheaper.
Try Hobby Link-Japan (hlj.com) or Rainbow-10. They may be able to get it to you more inexpensively from Japan than from a Stateside operation.