Other sites with B-scope scores are superbcert.com and diamondbrokersoffl.com. (You have to ask for them at dbof.) I haven't decided yet whether to limit myself to stones with B-scope scores yet. There are some criticisms of the B-scope that seem to be legitimate, but I still tend to think that a stone with great scores is a pretty good bet. Dave Atlas seems very highly regarded and does not go in for scare tactics like Rockdoc (gemappraisers.com). I would think that with a good independent appraiser who is willing to give you a frank opinion, there would be no need for the B-scope at all. The thing is, if you are not yet pretty confident in the quality of the stone before getting it appraised, you might have to be ready to go through a few appraisals before getting the right stone. For larger budgets this would not be too much of a problem, but multiple appraisals would eat into a smaller budget pretty quickly. However, since you can see the stone in person, you already have a pretty good idea it is nice, so I wouldn't get too hung up on the B-scope. If the B-scope is useful, it is more useful for online shopping.
If you can't get an independent appraisal before buying and you can't return the stone, that sounds pretty fishy.