I know your frustration
I am 6'7" and have had a hard time finding a bag. I finally found a lightweight down mummy bag for bike travel and I guard it with my life, as I don't know that I would be able to find another one. For vehicle travel, I use a Caribou Mountaineering bag. I don't remember the model but it zips to a Caribou coupler that holds two Therma-rest camp rest pads. We have been using it for quite a few years and it has worked great. It basically makes into a king size bed, yet breaks down to a small bundle when stored. When travelling, we keep the bag and coupler zipped together and just fold it into a stuff sack and the pads go into their stuff sacks. Not even sure Caribou still sells my set up but if they do, I would certainly recommend looking into it.
The Wiggy outfit seems like a good alternative if the above is no longer available. In fact I bookmarked the site just in case. Good luck in your search and let us know what you find.
Mikey