What is the "bromide" restrainer used in lith printing?

I am using the Moersch SE5 lith kit and can't get a hold of more Part D which is the bromide restrainer from Freestyle (back ordered with no ETA).

Is this potassium bromide? If it is, can I get it elsewhere and what proportions do I mix it (weight/water ratio)?

I just looked up the MSD sheet on part D: It is Potassium Bromide 30-40% weight and 0.1-0.5% Nitroindazole.

Is the Nitroindazole a preservative and is it important in the restrainer process?

Silly question but is there an easy way to get a mixture of around 35% Potassium bromide mixed up? Do I really need to weigh the chemical and water? How long will this mixture keep (does it oxidize or go bad in any other way) and what temp water do I need to mix it up?

Bromide solution as a simple salt with one-atom ions will keep indefinitely.