Is there a place online that I can look up how much 1099 income was reported by clients?

No, there's no way to look that up, other than in your business records. You don't need 1099s to file, just use your records.
Is there a place online that I can look up how much 1099 income was reported by clients?
The 1099 should correspond to your records anyway.
Reply:By whose clients? By your clients? If you issued the 1099s you should know that answer.