1) You can buy both kinds from the special armorsmith (random chance, not cheap)
2) Steal from a lord (1 or 2 have the berserker armor) that is your prisoner
3) Loot it after a battle (if the enemy troops were using it, like berserker or norse bannerman)
I'm reviving this thread for another question:
I don't want to start a new game right now - is it possible to add a dog into a pre-reforged savegame somehow?
Thank you, that works!
Enabled cheats, enabled cheat menu, talked to caio, kick him, lose 15 relation with him tough, he joins back immediately, pause bug removed!
Just to say for anyone reading it here, Sorta gave us a fix which worked for me.
[quote author=Sorta]
Kick Caio or whatever the Roman dude's name is out of your party and accept him back in when the event triggers. This worked for me, at least.