It is offered occasionally on eBay. It gets very large and is easy to propagate by leaf cuttings.

Here is one I started from a leaf. I will try and post my biggest one later today.
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Here are some more images of my big Challenger outdoors and indoors blooming.

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I just found the Challenger at a local nursery in Santa Fe, NM. SF is at 7,000 ft and very dry. How would you recommend this plant be pot grown? (water, soil, etc) It is far too bright for it to go outside. Some of the leaf edges are already browning and it is in part shade. I think it must be a water issue--too much or too little? Treat like a Rex??

I lost my big one after a few years. Still have a couple very small ones today. Lost my mojo I suppose.

I guess there is no way to raise the humidity in Santa Fe (visited there many years ago) but humidity helps keep browning edges at bay. Perhaps a small pond/pool to put the pot in (out of water - maybe supported by some stone/stones) to keep the humidity up?

I use Miracle Gro potting mix (not the water moisture mix) which is usually fast drying. Move to bigger pots as it grows. Water well and let it dry some before watering again. I kept mine under the shade of big poplar trees but it can take some sun for best growth. Use slow release fertilizer to give it some nutrients too.

Here is another giant (darker green and lower growing but still a giant) called 'Maggie Nodal'. This picture is from last year and is in an 18 inch container. It also has two begonia 'Big' plants in with it (the red blooms) and a much smaller Gryphon. The Persian Shield (purple leaves) is in another 18 inch pot behind this pot and has Sinbad and Medora in it as well. These got full sun until about 2 PM after the sun went over the deck.

Fingers crossed. Thanks!.