Hi Bob,
Thanks, will check this eve.
We do a hose through end screw, on the website it's called 'Aluminium Pole End Screw Type1'.
I'm not sure what the ID of the top section of a harris pole is? The shaft on the end screw is approx 19mm diameter.
This is supplied if you choose 'Quick-Release Clamp' for pole connection, which will then give you the total price.
Paul