How should you write the consignment agreement? You shouldn't. Find a lawyer who understands these kinds of royalty agreements and let her do it. The reason, as you've no doubt found, is that the wording can involve intricate calculations.

Maybe $0.99 per unit is fair compensation for the initial introduction to the TV producer, but does it continue to be fair the fourth, fifth and sixth time the producer features the inventor? Does it matter if the TV segments are new segments or repeats of the same segment involving the inventor? How deeply do you want to be involved in the inventor's business so that you can verify that you're being paid what you're owed? What kind of reporting do you want to see? How often?

Improperly drafted language can raise a host of misunderstanding -- or worse, cut you out of compensation that you're rightfully entitled to. Leave this one to the experts.