Flying Tiger had ring organisers for sale when I went in for a browse over the weekend. They had a hologram version in personal size, and red/black/blue in A5 size. They had basic refills and were, as is the norm for Flying Tiger, not at all expensive. They are not going to last twenty years and are by no means an investment buy, but would be perfect for archive storage, travelling, projects, or beginners.
I did not check whether any of them are Filofax-compatible but Flying Tiger’s binders usually are.