Any local machine shop should be able to do that for you.
They may need your old gear knob or to measure the thread on the end of your gear stick to do it. It's not a hard job at all, especially if as you say there is plenty of material there.
Because you are in South Wales it may be worth hooking up with Baz (Mad Welshman) as i know he works in a place with those facilities. If not just look in your yellow pages for a local machine shop.
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