Tonkin boo and Tonkin cane are two different products.
The (flat) stuff listed above from BRW is not Tonkin, but is the Taiwan bamboo. Still good stuff, but seems to be a high demand item. They only import so much per "season", so it helps to let them know you need some in advance. Give Mike a jingle at Dryad Bows. Maybe you can sweet talk him into selling you some.
After Dean put out his Hunting The Bamboo Backed Bow video, suppliers have been selling lots of flat boo.