The men-at-arms in Udgaard have good armor.  Often, someone
kills them for one piece (a ring, say) and leaves the rest. 
As some of them wield polearms (their lances are classed as
polearms), you can grab those from the ground.  Not all the
time, but often enough.

That said, in my personal opinion, the polearm is not all that
great a weapon for a shaman.  You lose the benefit of using a
shield, for starters.

However, if you are ok with that, then enjoy your polearm
wielding shaman!