You actually can buy them online, or even in a physical store. You can buy Wii points cards. These can be bought online (Amazon.com, Target.com) or in the stores.
It's the same as buying them on the Wii, 100 points will cost you $1 USD, and they are only available in amounts of 2000 points, (so $20).
Glad to hear you finally got a Wii!!
Is there another way to buy Wii points besides doing it using the Wii itself? Can't it be done online? I thought I'd read it wasn't secure to buy them using the Wii console, that hackers could get your credit card number or something. Can anybody tell me more?