Some Providers require references, others want to verify that you are who you say you are. Others don't require any of this at all, visit this site, your local site and the individual websites of the Providers they will tell you exactly what is and is not required.

Some ladies that normally require another provider's reference will sometimes accept employment information instead. They just want to be able to verify that you are indeed who you claim to be. Any reputable provider will do so very discreetly if this means actually contacting you at work.
Another option is to first use an agency or a provider that does not require a reference. This may not be your first choice but at least you then have a reference for the lady(s) that you were more interested in.  
Remember that a provider's screening process is to establish a certain comfort level before she must be in a room alone with you.  She is more likely to be concerned with personal safety than potential LE threat.  
best of luck to you