Here's one with the door at the thin end at 4ft x 8ft (122 x 244cm). A door opening outwards helps things along, as do shallow sinks. Another tip is to nestle the sink and toilet cistern into niches in the wall which means them stick out less into the room. The minimum width you can get away with is about 4ft (122cm).
Wouldn't this be wonderful? Our home is 116 years old and this toilet would be such a fitting addition, not gonna pay over $5000 for it though. It's so expensive that it tells you how much the individual parts are and not the thing as a whole. lol