I don't know the exact dimension of a F1, but I do own the Spec-ops brand sheath which is made pretty sturdy and quite well designed. They come with pouch at the front and two different lengths. The drop-leg design is comfortable to wear than most sheath riding up high on belt, and the plastic insert in the sheath is also a nice touch.
Heinnie Haynes in the UK have two leather F1 sheath designs from Fallkniven. I realise it would mean ordering overseas but as you are in the EU it should be fairly inexpensive http://www.heinnie.com/fallkniven-f1-open-leather-sheathhttp://www.heinnie.com/fallkniven-knives-f1-full-cover-leather-sheath