Investors & landlords

How do I calculate our cost basis for YHOO shares purchased as part of an ESPP?  Does anyone know of a website or other tool that would list historical data for this?  I know the date the shares were purchased, but not the amount.  Thanks. 

 

FWIW, I also did not receive a 1099-B since this wasn't a "sale" per se, but it sounds like TurboTax is guiding me to enter it as such.  My cost basis is lower than the distribution, as the shares were purchased in 2009.