Yah, I'm self employed too.  One thing that has worked for me in screening is presence in industry trades.  Have you written articles?  Taught classes?  Given presentation at conferences?  This will help you if it's web searchable.

Have you tried contacting date check or rs2k and asking them?

There ia an alternate method of screening available on most verification sites where a provider vouches for you. So you will need to find a provider that is a member of one of the verifications sites that is willing to see you and then vouch for you. Obviously, she will need to screen you herself in some form but it should do the trick......

I am sure that you are not the only person who is self-employed.  They have their methods for verification.