Is this for brief (few hours) rally sleeping or for multiple day use? If it's for things such as the BBR I used to use a couple of different types of bivi bag, one flat zipped gore-tex bag then a Snugpak Stratoshpere single hooped bivi bag. I then went down the route of purchasing a cheap (£12) single skin, twin poled, sewn in groundsheet tent from ebay/Amazon. Quality ain't great but I gave it a spray with dome Fabsil the week before and it was only ever for a few hours single night's use.
The advantage is you can quickly dive inside with your helmet and gear then get your head down without being squeezed into a bag or even sit and re-plan the next day's route if you need to. During the 2016 BBR I slept in a field less than a mile away from a 24hr fuel station near Hale in Cornwall then bundled it up, rode back to the fuel station and chucked it in a bin