We are a couple of those weird lightweight freaks who try not to tour when it's below 45° and raining. So for us, a small, breathable, inexpensive and versatile hi-viz wind shell works for the upper body, while leg warmers, booties, and dry suit leg seals keep the lower body feeling good. For us, cycling is a much too aerobic activity to wear waterproof garments. I've tried them, including the Marmot Precip, but had to take them off within 5 miles. Precips work well for us when hiking.
Voler: Jet Men's Wind Jacket

These items, except for the leg seals, are things we would have with us whether we thought it might rain or not. So no added weight, cost, or bulk.