This is presently in a gallery exhibition with the "Makers Guild Wales" at "Craft in the Bay, Cardiff, CF10 4QH". It is currently available for sale to the best of my knowledge although it may have sold already. You can telephone Craft in the Bay on 029 2048 4611 (GMT hours 10AM-5PM broadly MON-FRI), and they will be able to complete the sale directly.
When ordering from the Makers Guild over the phone to speed up your request if you provide them with the following information "I wish to buy a piece from the gallery, made by Selwyn Gale, it is "Sapphire & diamond wave ring, costing £1460 and I don't know what the SKU is sorry." - that should ensure you get a crisp and sharp response.
It may be possible to purchase this item from the Makers Guild online shop - which as of July 2020 is under construction at https://www.makersguildinwales.org.uk/.