Maybe not quite what you have in mind but ...
I use / carry a ripstop 'army poncho' (about ~£15.00 from lots of military supply places). It's not ideal for riding in, (actually it's kinda rubbish for riding in ) but you can at least tie / tuck it up a bit to make it more manageable on the bike, (and a bit more protective off it).
Where they are genuinely useful tho' is sitting out brief, grotty spells of weather if there isn't much [other] shelter around and you get caught out. Definitely saves you getting too chilled and wet waiting for stuff to blow over, plus it's something to sit on. No arms tho'.
I've always got one in my bag for my winter expeditions (an' I also carry bothy bag now too, but that'd be impossible to ride in! ).
That ^ was about 30 seconds before a particularly vicious hailstorm pinned me in against that embankment, but I was still 100x more comfortable in it than I would have been without it.