The simplest way out would be to buy a Firstgear, Joe Rocket or your choice of textile jacket and pants, they come with armour and the better ones are waterproof and vented too, so they become permanent riding gear. I've got a couple of Firstgear jackets and pants and they come with soft armour but you can buy the hard armour from them too. I've worn them on several thousand mile tours and it beats carrying and trying to put on a rainsuit. A friend of mine got tapped by a car and went down on the Hutchinson River parkway wearing a textile Belstaff with armour and between the full helmet and the jacket it saved his butt.

NYPete