I have the same question for the Biorb tank models please (although I can not get them locally so they would have to be brought in from overseas suppliers which would take longer).
I do not recommend the Baby BiOrb for bettas, and I think the normal sized BiOrb would probably have the same problems, namely, it's very awkward to position a heater and the cord shows. Also you need to get a cover for the tube the bubbles come out of, as bettas are curious enough to wedge themselves into them and die. You also cannot position them too close to any windows, as they act as a magnifying glass for sunlight and can start your furniture on fire.
You're best off buying a plain rectangular 5 gallon glass tank and glass cover, and buying the filter and heater separately.
The ideal type of betta filter is a sponge filter (they look like this: http://www.kwzone.com/products/acces...e%20Filter.jpg
). If you decide to get one you'll need to also buy an air pump with adjustable flow and some standard sized aquarium air tubing. If you want to position the air pump below the aquarium, make sure to also buy a Non-Return Check Valve to prevent water from getting into the air tubing. These filters are very low maintenance. Just squeeze them out a couple of times in old tank water when you do water changes.
You can find cheap aquarium heaters from sellers in China on auction/sales sites like eBay.
If you want to grow live plants you'll need a specific type of lighting. If you don't want to do that, you can buy any type of aquarium lighting.