Here is great a poncho made with the very strong, durable and shiny Opalo material.
With the black colour, you may also decide which thickness you want, the 700 g/m2 being the standards. Dark olive green and black is also available in 1000g super thick fabric.
A poncho of size 54 is about 114 cm tall (from shoulders to hem), the shoulder to shoulder length is about 75 cm and the bottom of the poncho is about 115 cm wide.
The poncho is regularly so tall that it reaches a little bit below knees. You can also request extra length to make it longer. Added length is about 30 cm making the shoulder to hem length about 146 cm. The blue poncho in the pictures is standard length and the red one is the longer one.
There doesn't seem to be much difference between M/52, L/54 and XL/56 so would suggest getting the one that I have in stock.