Let's see, you find out in which countries it is illegal to tie phone sales to contracts only (clue: most of Europe). Then you get a buddy there to buy an iPhone 4s for you without a contract and fedex it to you. Meanwhile, you go to Vodacom and get a contract with a fat data cap and the crappiest phone they will give away for free. When your iPhone arrives, you throw away the crapphone, cut down the sim to a mini-sim (templates are available on the internet), put it in the iphone and bob's your uncle.
Or you could wait for Vodacom to announce that they are now carrying the 4s. Which may just happen a week before the announcement of the iPhone 5. Or 6.