I think those would be tough to find but not impossible.Reptile breeders have snakes die all the time.I don't know if you have any in Norway.
There also may be problems with shipping some wild skins internationally if the species are protected.
The problem you have with very wide snakes like you mention,is that if you get a skin long enough for your bow limb,it is so wide that you will only be using a small,narrow strip and a lot of the pattern that looks so neat on the snake,will not end up on the bow.Snakes like that can also cost $100-$200 per skin,not counting shipping.
Puff adders are more common and may be easier to get and though they aren't as colorful as Gaboons,their chevron pattern might work fairly well on a bow.