I have been looking for these as well and found them last weekend at Covington's in Rowlet. I have not grown them before, however.

I haven't grown them myself, but I saw them in the Overton Plant Trials in 2014, and then again in early fall that same year. They had them in both sun and shade, and they did well in both (but since I have shade I was more impressed by their blooms in the shade areas).

Thanks to this post I recognized them while at Bandara Rd. Rainbow Gardens in San Antonio. They only had two in half gal. pots priced at $5.95 and I got them both. The tag in the pot simply said 'Big Rose" and nothing else. They have the bronze leaf.

The staff didn't seem to know anything about them, but said they'd be getting more in. I'm really happy to have them. There are two plants in the pot. Maybe I'll take some photos later. Will keep you posted on how they do in my part sun locations.

I hope those looking for them will find them.

Here is a photo with a three inch pot of the regular wax begonias for size comparison: