I agree on the Integral bivies and consider them the best overall that I have seen or used; I have a Unshelter, Bugaboo-eVENT and South Col-eVENT and I never leave my vehicle, horse, plane or boat without a bivy-tarp in my emergency pack.
Just did a trip in northwestern BC, it poured rain and we got soaked while looking for a RM Goat for my buddy. I did not care, even in that remote locale as I have bivy-camped in such situations many times and know I am safe and wsill be warm and dry as soon as I set up my rig and change into my spare merino base layer.
I like the look of the new "Three Wire Bivy" from BA and I might well buy one for winter hiking and short camping treks, probably get a bright coloured siltarp to go with it. Nobody makes exactly the bivy I have a mental image of, but, that one comes very close.