Claim it all - I've been doing this for 9 years & not once has the amount of money I've recv'd 1099's for been anywhere close to the amount of money I recv'd from sponsors.
Think of it this way - let's say you made $10K last year from sponsors but you only got in 1099's totaling $5k & that's what you put on the tax forms - if the gov't ever looked at your bank statements & saw the extra $5k, how would you explain it?
It's the sponsor's fault for not sending the proper forms out to you, so claim all the money & let the IRS worry about them
