a VirtualTourist member
Is there a fishing tackle shop in Borgarnes that sells worms for Salmon fishing?
Been too long since I was in Borgarnes, but here is some overall fishing information for all of Iceland including the Borgarnes region. Trust that no one will let you get a fishing permit and not inform you as to bait availability. review this and its various pages. Find a farm in the region that does fishing trips.
.....and finally this one, which may be right up your alley. And don't worry, you will not be wanting for bait. if you go with a local, they will make sure you have it, and if you go solo, it will be easy to find.
Good luck and enjoy my country.........d:o)