Hi,
Welcome to the forum Barry.
Have you tried eBay Barry? If you can't buy a suitable riving knife how about making your own? Here's riving knives I've made over the years and it's not difficult. Good on you using a riving knife though because I see many YouTube videos showing big saw benches being used without riving knife installed which is highly dangerous.
The black one is bought new through eBay.
Kind regards, Colin.
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