Throwing axe. As far as I'm aware the only way to still get one of any quality in the recent versions is to start the game with the shelter scenario and have one laid down as one of the useful items before you.
Getting any of the cultural weapons in fine or better is indeed annoying. The only one's I'd count on are fine Northern Spear and maybe fine Northern Knife.
I'd actually suggest to:
Make northern settlements spawn occasional masterwork melee weapon, just like they currently do with bows. Their current weapon repertoire is pretty restricted already (northern spear, staves, tridents, northern knife, fisher's knife, handaxe and maybe regular knife and woodman's axe) so it shouldn't be a biggie.
Give Kaumo a similar weapon inventory as above, just replace the two Northern melee weapons with the Kaumo ones.
Add Ango and Skarmasaksi to regular repertoire of foreign traders. I have certainly not ever seen them carry any despite going through what must be several hundreds of them in recent (post Steam release) versions. Both weapons are clearly foreign in URW as they have loanword names (Angon and Scarmasaex).