They are usually a limited single run, however sometimes if a figure is popular enough they may do another run or re-release. Current example is Sinon's Figma, she's getting a second run right now. Mind you the time between runs can be years. It's generally a good rule to not expect a re-release. Also some manufacturers have polls for their next releases, but my power level isn't high enough to know whether they include re-releases.
Edit: Oh yea, let me know how you're cloning goes, I was actually thinking the same thing. I've got some experience with silicon pour molds and 35mm models, nothing fancy like plastic injection though. Hope to see what you can do. (Personally I'm thinking about crafting transparent riot shields)
Ah, what a shame, although I guess it is to be expected since the anime market is so diverse even though it commands a very small amount of capital.
Riot shields would be very easy. Go to lowes and pick up some thin 0.1" plexiglass and with a heat gun, gently heat the plastic and let it melt over some kind of curved surface. Use as little heat as possible as plexiglass is catagorically thermoset and will easily char and darken if heated too much, even if the temperature itself is low. for the handles just find some kind of thin plastic wire made of a thermoplastic (plastic welding rods are probably ideal) bend it into handles, drill holes in the shield for it and fix in place using slow setting epoxy. It is critical to use slow setting because it provides the necessary strength to make the bond strong given how small the gluing surfaces are. Paint.
Since I am making "new" figures, I decided I would make the figure modular so you can change her appearance easily too look like any anime character with the right face and hair exchange (assuming her scaled height is the same). My current plan so far is to use my existing parts and 3D printing to make some parts which I will clean up with a dremel and file to a precise shape, make a mold of it using silicone and try making a figure using 2 part thermosetting plastic. If I get the tolerance right, I will use that mold. If not, I'll scrap it and try a different shape until it fits. The joints are probably going to be the hardest part to get right since the plastic needs enough flexibility to retain parts, but loose enough to move or be taken apart. I'm also thinking of casting it undersized and using the "joint tightening" techniques to build up material and get it to the exact tightness needed.
Ideally once I get the proper dimension figured out I will use injection molding (as it is much cheaper than buying a two part mix) but I need to figure out a method to make a high detail metal mold of these plastic parts. Although it will be good practice as I plan to achive that level of accuracy sooner or later to build myself my own 5.7 handgun off someone else's duty handgun anyways.