Most historians claim that viking sword scabbards were made from linden (lime) wood covered with thin leather, (but most historians claim cuir bullion was made by boiling leather in oil, I tried it and have had serious doubts anything historians say since then.). While there have been a few finds with this construction they have been from the graves of Kings/Cheiftans. Although there is no evidence for scabbards made entirely from leather in the vike period, logic suggests they were made. I've tried making a leather covered plywood scabbard but it was a pain and looked crap. Here's one I made from 7-8oz veg tan with neutral shoe polish as a finish for a 38" sword weighing 4 lbs. So far it's survived 16 years of everything the British summer can throw at it (rain, hail, snow and the occasional scorching hot day.) and the occasional blow from swords, axes, billhooks and flails. At 2 1/2lbs I'd worry more about the sword being too fimsy rather than the scabbard.