I thought about John's suggestion about the construction paper gussets and played with it. I wrappred strips of wet silkspan around the joint, dried that will the heat gun and then soaked it well with thin CA. After it's dry it can be smoothed out with sandpaper.

I'd call this experiment a moderate success. There's no doubt it's much stronger than the unwrapped joint (which isn't terribly strong) but not as "unbreakable" as I was hoping for. It breaks about as easily as a wishbone. Maybe I'll try a joint with a simple epoxy coating. I'd like a joint that is strong enought to deform the bamboo before breaking at the joint.