Hi @Jessie987,
A warm welcome to the Bunnings Community, and thank you for your question.
It's hard to say what exact spindle to replace your existing one without being able to compare.
My suggestion is to bring both spindle back to your local store, return the one that is too large and have the Plumbing Expert assist you with matching the old one up with a replacement.
Something like this Shaw & Mason Chrome Plated Wall Spindle looks like it should work, but the thread size and length of the spindle will need to be physically compared to confirm.
Let me know if you have any further questions.
Jacob
