I'm not familiar with the RSM...
I have 2 ballasts that will work, but they are from a retro kit, so they are each in a bulky housing.
I'm guessing you want just the bare ballasts so they fit inside a hood?
Have you tried just going to an electrical shop with part numbers and specs and seeing what alternatives they have? Really the only thing is trying to find one the same physical size so it will fit nicely.
For example, Grainger has a ballast for $40.
https://www.grainger.ca/en/product/E...277/p/GGE4KGG2