provide LBS of food products purchased?

Interesting challenge - Two thoughts come to mind: 1. Would it be feasible to use post-mark up prices for all your food items? That would solve this vendors problem, although it may create others elsewhere. 2. If this vendor purchase isn't a huge part of your overall purchasing, I think you could estimate his prices (he or someone in the industry would probably be willing to give you a rough % markup) and explain to the reviewer your process for doing so. If you estimate conservatively and your process for doing so is transparent, the odds of the reviewer agreeing with your approach increase significantly. Good luck with it!