Keikoyari (training spears) are not obtained easyly even in Japan. The author saw a kamayari for sale in a budô equipment shop in Tôkyô just once. And there is only one maker/distributor of wooden weapons who sells kamayari and suyari (but only 9 shaku long) through his webshop. Recently he ships the spears to destinations outside Japan as well, but I fear the transportation might be even more expensive than the spear itself.
So in the end you have to ask a carpenter to build a spear to your specifications. Or just do it yourself. Don't worry. Building a spear isn't that difficult. On the contrary it is a lot of fun, at least for me.