With valuable eggs, I would not let two broodies share a nest box. Many people do and don't have problems, but sometimes they fight over the eggs and break them, or sometimes one will kill the chicks that hatch under the other. It is not that problems are guaranteed to happen, just that they can happen. Same thing with two broodies raising hatched chicks together, whether they hatch them together or if they hatch separately and then share the same space trying tio raise the chicks. Often it works out great with no problems, but sometimes the hens fight over the chicks and chicks get hurt in the fights or sometimes one hen will try to kill the other hen's chicks.
I see a couple of basic options for you. One is to break one hen from being broody and let the other set on the eggs. The other option is to try to move one broody to an isolated pen where she has a nest, food and water, and enough room to get off the nest and go poo. But she is locked in where she cannot get back to her old nest. Leave her locked in there until the eggs hatch. If you move her, move her at night with as little light and commotion as possible. Do not give her the valuable eggs immediately. Let her set on some eggs you don't care about or maybe fake eggs for a few days, until you are sure she is staying broody. I think it helps to keep the nest pretty dark. That seems to calm them. I'd go so far as to suggest you leave her locked in the nest itself in total darkness for the first day. Broodies usually go long periods of time without food and water, so it won't hurt her. You might let her out late in the day, just before bedtime, so she can eat drink and especially go poo, but leave her locked in the enclosure where she cannot go back to her old nest.
The hen you leave behind will probably stay broody, but either might break at any time. They have been broody a while. Since the eggs are valuable, I'd suggest keeping the good eggs in the incubator until lockdown, then put them under a broody if you still have one. Keep them on fake eggs or eggs you don't care about until then.
Good luck.