It's very complicated and quite 'messy' when it comes to the phylogeny/genetic trees. Most of the time, researchers only need those 20 fish or so once every few years, if that. Sometimes they need to interbreed these different fish to glow green and red. There are literally tens of thousands of types of fish that have to be kept. As an example: Jackson Labs has mice ready to order to the specific genotype that you want and it gets very specific [0]; zebrafish aren't quite at that level yet, but are getting there.
But the effort is worth it. Zebrafish are a great animal for studying neuro development and many other things. Many of the proposed treatments for ALS, Alzheimer's, Parkinson's, etc. got their start in zebrafish and in studying how those little vertebrates function. The effort will save countless human lives.
You wouldn't even need a different specie to bypass the money-grabbing, you only need a new facility, your own certified processes, and some clout in the industry (read citations). Hell, you could start with the fish from the expensive vendor and sell the offspring (I think, unless there's a licensing agreement involved).
> the facility in Europe had suffered a fire that required them to stop production for 4-6 months.
This sounds very strange, unless you want to artificially create a scarcity in the supply of an animal that anybody can breed by thousands in their living room. You don't need almost any space to breed this fishes, and aquariums can be moved right?. 6 months seem too much.
I wonder why nobody has tried with another of the 100000 species of fish with transparent embryos and bypass this money-grabbing structure.