There are loads of options, depending on the type of training. A stock cane from a tractor supply place or eNasco is a cheap and durable crooked type if that is what you are looking for.
There are also a variety of 1x36" dowel available in hardwoods that should be suitably strong if you just need a simple hanbo design with no parts to fly off. Examples good woods are oak, hickory, osage orange, purpleheart, cocobolo, jatoba, chinese waxwood and American hornbeam. They are all strong and durable, but have different properties of density and flexibility. You might want to experiment.