Yes, those Kronos caliper hoods are pretty much unobtanium, these days. Plus, you'd pay big time if you find one in decent condition, if you can even find one. I haven't noticed any good Kronos brakeset stuff for sale out there, for a long long time already. Mostly just the brake levers, and most of them are trashed already.
If you have a good one to use as a pattern. Maybe you might consider molding them yourself in silicone rubber, if you might be up to it?
If you check around, there are lots of molding kits available for hobbyists.