I'd like to chime in for Specialty Insurance. I've used them for many years. They don't charge for certificates and they are very prompt. I have made more money than I would have had I not been with them: There have been numerous times that a client has told me at the last minute that they need a certificate and Specialty got it to me. Most gigs won't let you work if you can't produce a cert if it's required. I would have lost a number of jobs if it hadn't been for the speediness of Specialty's staff.
One time in particular the co-coordinator wasn't told that a cert was needed until the morning of, and she called me at 5:30 in the morning (gig was at 10am). I didn't figure anyone was up at that hour at Specialty, but I went online anyway & filed for a cert. Within an hour there was the cert in my inbox!!! And I got a nice 3 hour job I wouldn't have had.
Costa Mesa, CA