Here is great a poncho made with the very strong, durable and shiny Opalo material that has opening only in the bottom and in the head.
With the black colour, you may also decide which thickness you want, the 700 g/m2 being the standard. Dark olive green and black is also available in the 1000g super thick fabric.
The length of a size L/54 from the shoulder to the hem is 127 cm. The width of the poncho is about 70 cm on the shoulders and 118 cm in the hem. There doesn't seem to be much of a difference between M, L and XL sizes.