As far as I know the Winnebago Era 170C (made 2016-2017), and now the 170M (changed the foldout couch to a murphy bed for 2018+) are the only ones out there.
There used to be one from Leisure Vans out of Canada, but they stopped making them when their B+ lines took off. They were the first (the 70C was a reverse-engineered copy), and I don't think anyone else has done it.
I love the B-with-slide... as far as I'm concerned it's one of the best designs for a couple without kids I could ever imagine... and I'm always amazed how unpopular it seems in the market.