If you are looking for a document provider with a pre-approved ESOP, ASC, FIS and FT William and possibly a couple of others have them. The IRS has a list of the cycle 3 document sponsors on their website. If you are looking for a firm that is sponsoring an ESOP document from one of the document providers, they are also on this list. If you look at the FFN for a document on the list, characters 8 and 9 tell you which document provider's document they are using. ASC = BH, FIS = 07 and FT William = FT.
https://www.irs.gov/pub/irs-tege/ppa_listdc3.pdf
You can get some of the other sponsorship lists here:
https://www.irs.gov/retirement-plans/list-of-preapproved-plans