From what I understand (please correct any inaccuracies):
The REPLACEMENT type of Antron Fleece is available on a limited basis... occasionally from the fabric mill that owns the license rights to manufacture it.
Years ago, the Pepsi Company bought the Antron Fiber Company. In order to cut operating costs, the new ownership cancelled manufacture of everything except carpet fiber. That included the original "formulation" of antron fleece fabric.
Rumor has it that The Muppets bought up every last available bolt of the original fabric. True or not, you can see the logic in that.
Another company (I'm assuming a fabric mill) bought the rights to produce a very similar fabric (similar because the original fiber was no longer available to make it from). That is what I call REPLACEMENT fleece.
This fabric's use in industry is no longer what it once was (I'm told it was used in cars? But I'm not certain about that). So the demand for it has waned considerably... making it something that isn't worth manufacturing in massive amounts. Thus our continuing shortage. And the reason its only made in smaller batches now.
The mill does runs of the fabric on occasion, and that's when it becomes available. So it's going to be a matter of keeping highly attuned to the folks at Georgia Stage (pretty much the only distributor that I know of) and plan your commitment in advance. If you place an order, there'll eventually be enough orders to justify a run.
Sorry, but that's the way it goes.
If you're in a position to do so, you can order an entire 50+ yard bolt of the fabric and have your own supply. A bolt costs about $600. But at this point, you'll probably be waiting on another mill run.
My other suggestion is to start looking out there... seek alternatives to make your puppets from. Because I guarantee you... this problem won't be changing any time soon being that it's only consistent use is by puppteers making Muppet-inspired puppets.