Not sure if this material is legal in Alliance, but in Amtgard thin core bamoo works really well for short spears/polearms. Make sure that the bamboo isn't cracked in anyplace for obviouse saftey conserns. Pay close attention to the joints of the bamboo. You'll find alot of your flaws there. Also stress test it to be sure. Place one end against the ground while holding the other end up. Then lean on your other hand somewhere in the middle of the bamboo so that it bends (Note that you should use a little bit more wieght as you would normally use on this weapon in Alliance type of combat). If it creates a visible crack it's no good.
Once you find one that's good enough, spiral wrap tape around any exposed/unpadded sections of the core to ensure that if in the unlikly event that someone falls on your polearm or what have you, the wood is contained by the tape.
You can find bamboo at just about any garden section/store. Got alot of mine from freddies some years ago.
B~>