Typically, the outcome of a bilateral monopoly is not neat and tidy, but is indeterminate, so we cannot tell what the price will be just by looking at supply, demand, and cost curves. This just makes sense. Both parties may grumble, but are still relatively happy. Unlike General Mills, very few produce suppliers command such a presence in the market that they can set prices or negotiate trade terms that differ from others in the industry. In a competitive market like produce, sellers are price takers.
Many factors explain why produce suppliers have little market power.
Second, produce production tends to be localized. Subject to protection by PACA, once produce is delivered to a certain point the shipper faces huge costs of moving to another market should the existing deal fall through. Third, the supply of produce is decided by the size of the crop and not by production-line decisions. Whereas a packaged-products manufacturer can slow production to create an artificial shortage, single growers do not have this ability. The net result of each of these features of growing produce is that growers must take what is offered to them.