QAV250 Aero Cover (snap-on)
These are designed to fit onto the spacers on a QAV250. The wall thickness is 0.75mm and both durable and leightweight. I've made two variants, complete covers or with small openings on the top. I use the variants with openings to enable some equipment to protrude from the sides (such as antennas etc).
Shapeways: https://www.shapeways.com/product/LM6WYKWQL
Weight is ~12g.