S
P
O
I
L
E
R
S
.
.
.
.
.
.
.
.
There's a halberd called the Wave which you can put together as well. I won't spoil the locations since you haven't asked, save to say that if you a) follow through on Haer'Dalis's quest and b) make sure you headhunt a certain rebel prince under the sea you should find what you need.
There's also the Silver Horn of Valhalla which you can upgrade using a beljuril and a diamond. Cromwell doesn't do this for you - a merchant in Waukeen's Promenade does (I forget his name, but he's just south of where the ore merchant is).