Here is a poncho that is especially great for cycling.
 
It is long and also wider than normal at the bottom.
The front of the poncho is closed with a zipper (about 1 meters down from the neck) and velcro all the way down.
The zipper has a velcro stormflap over it.
The hand openings are also closed with flap and velcro
Material is matte 350g Plavitex.
Available in multiple colours
 
On the photos above, the person is 171 cm tall and is wearing the largest possible poncho in size 4XL/62. I would say one size fits all, but I have provided the other sizes for selection as well.