I only just looked at the link that Lorne provided for the Recaro Seat Webbing. My seat padding support is indeed the same rubbishy item as sold on US Ebay.
Perhaps it is better called a spring mat than webbing.

A bit of a search found others for sale. This one from Pelican Parts.

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I love the description from https://www.akr-performance.com/p/recaro-seat-webbing-363738
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Why replace the RECARO spring mat under the seat?
The spring mat, also known as seat webbing, has the main function of supporting the foam in the seat. Over time and intensive use, the elastic and jute materials can weaken.

You will notice this due to the reduced support and comfort for the driver and passengers. Replacing the spring mat can breathe new life into your seat and provide the original support and comfort you expect from RECARO.
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Original part for OEM RECARO seats

This rubber diaphragm is the original part for many OEM RECARO seats as used in various Honda Type R models. They also fit various aftermarket racing seats. This part has been specially designed to meet RECARO's high standards and offers the same quality and performance as the original part.
I am not sure that I want something that offers "offers the same quality and performance as the original part."

At least AKR Performance are a little closer to home in case I decide to replace the rubbishy spring mat with the same rubbish.

Peter

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