First let me say I have wanted to do this since before I knew Ron Paul.
Second let me say it's not really possible due to 2 reasons.
1. All Islands are part of some country, and the country that owns a Island will normally only let you lease or rent it, only a few country's let you "lease for life" like Fiji.
2. There is more to starting your own country than getting a Island and saying "i'm my own country". You have to get all the countries to accept that you are your own country.
If someone TRULY wants to do this I will be willing to contribute, but we will have to get the money to "make a island" either a floating one (like a boat) which is looking into being done by a few companies, or Island made of sand and rocks that is compacted so that you can build on it. Both are VERY expensive, but I bet for 20 Million we could get a better "floating island ship" but last I heard they were only down to 10,000 a square foot which is only 2000 square feet (not much).