I am looking for a new waterproof jacket after my Montane Featherlight started to act like a bin bag!
I am after a jacket that can be packed down to put in a jersey pocket.
Do you have a budget at all? Presumably, after your bin-bag comment, it needs to be breathable? Does it need to be cycling specific? What about pockets, etc.?
Have a look at Marshall leisure. I've bought one of these Dare 2b Mens Retouch Jacket for just over £30. Its waterproof and windproof and packs away to literally the size of a tennis ball.
Re above - its not a cycle jacket just a waterproof but it's served me well.