OPK refill

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Hi guys. I'm from Australia and I bought these from the local Coles supermarket.
Was my first time using them but I managed to detect a surge on Saturday.
I now only have 4 sticks left so I'm wondering where I would buy refills?
Or should I just buy another box like this?
It cost around $35.
This seems a lot easier to read than the regular strips.
Any fellow Australian's?