I have never had any luck purchasing fish off the internet... Personally, I think it's not really worth the hassle and extra money to ship it... Good luck to you with your beta though!
I don't think that I would try this. It sounds extremely expensive given the issue of rapid speed for delivery. They would require enough water and air for gas exchange. I think it sounds very stressful in transit which may actually kill the fish shortly after you got it. Unless there is someplace very close to where you live, the long stressful transit time doesn't sound worth the expense or risk.
Betta fish have a labyrinth organ so they can breet air like we do and the a use to living in small bodies of water because they are found in small puddles in Thailand and other regions of South-East Asia. So I think you sould go ahead and get one. Go to http://search.ebay.com/Betta-Fish_W0QQfkrZ1QQfromZR8 For a nice fish.
