I use carbon steal, it will not bend without a lot of effort, wire from my local hobby shop, the RC crowd use it for linkages in planes, boats and cars. It comes in a multitude of gauges so take a figure or sample with you when you make your purchase, the only draw back is you will need some small bulk/bolt cutters to cut it, it is hard stuff, side cutters wont do the job and will be ruined very quickly.
I have a small bench grinder to grind the end to shape so it would be handy if you or someone you know has access to one, a 100mm hand grinder will work and so will a Dremmel. I also use a hammer and anvil to flatten the ends and shape blades with my Dremmel when required, a few tools and you can make any sort of spear or pike.
Hope this helps if you go the DIY route
I would opt for 300mm bulk/bolt cutters but this is the sort of thing you're looking for