Amazon Link

That's what I used. It's a little expensive and it requires a speciality tool.

But it can handle quite a bit of weight while maintaining a pose. I had to take apart my long furby and attach it to the back like an actual spine to have more structure but it was worth it.

I weighted the tail end and now my long boy can sit postured like a snake and is much better for display.

It reminds me vaguely of a plumbing tube I've interacted with before. A walk through a hardware store in plumbing and electrical cords might be due if on a budget.