I have a Next PX 6.0 mountain bike. It did not come with pre-installed mounting screws/threads for a bottle cage. The frame has large oval-shaped tubes, so many attachments that come with bottle cages don't work, since they're not big enough to wrap around the entire tube.
My current configuration is with cable ties, but they keep breaking. The bottle cage is currently only attached by one cable tie, as the other two have snapped off. (The bike is hanging from the ceiling, which is why the orientation might look strange.)
Are there any options out there for a more permanent installation of a bottle cage on this bike?
[UPDATE: I gave this bike away when I graduated from college, which was before I got around to attempting any of the solutions offered here. But, if you have a similar issue, the answers/comments here should still help.]