I've been using this one through 2 winters, http://www.rivbike.com/product-p/ar1.htm
Bought the Sou Wester locally , Grundens commercial fisheries foul-weather gear is sold world wide.
Grant had their cape made for RBW by them.
(I have 2 front Panniers one has the cape in it, if I'm not wearing it)

These are sewn, on order, in Eugene.. http://www.catoregon.org/cat-store/ lighter fabric..

they will sew up a 'hunchback' version, for backpack wearers.

those arm holes in the Posh-tweedy one are unneeded, You just flip the hem over your shoulder.
[ besides I think a Blending into the surroundings color is the Last thing I want on a dark wet ride]

the shape is different, but the cape does not make you wider, will it slow you down?, IDK.

My pace into a 'pineapple express' storm with a 30 knot headwind is not fast anyhow..

then the rain trousers come in handy.. wind blown rain..

Portland is sheltered, inland.

rain from above and my feet and legs are OK.( My Arms are an Awning.)

though going faster, YMMV..

My Bike has been set up with the Lights Lower so the cape does not cover them.
fork crown and Rear of rack.