Read Brewer's posts on how to DIY. Or use this approach:
I assume "no downside risk" means you can't lose nominal dollars. Suppose you have $10,000 to invest.
1) Buy a 10 year treasury strip, they were trading around 70 last week. U.S. Treasury Strips - Markets Data Center - WSJ.com
so you put $7,000 into a bond that will be worth $10,000 10 years from now.
2) The remaining $3,000 goes into Vanguard's Index 500 fund.
3) After 10 years, you have a guaranteed $10,000 plus something. The "plus" part will be larger or smaller depending on what the Vanguard fund does, but it won't be negative.
You will have a hard time finding an indexed annuity that can compete with that simple portfolio.