Hi @DJB67
I an just a customer like you
You would have to purchase one unfortunately.
This is the one that seems to get the most recommendations on the forum
https://shop.glowmarkt.com/products/display-and-cad-combined-for-smart-meter-customers
This is an alternative which is basically a Chameleon IHD7.
https://ivie.co.uk/product/ivie-bud/?gclid=CjwKCAiA9ourBhAVEiwA3L5RFrdyDaoqOvDzm1Tits6J_AdNTewNnkx0HxEXeu2R3Q8tzNNhSrPpGxoCnkIQAvD_BwE
Both of these are better than the IHD6.
The only obligation under the legislation is that suppliers have to legally provide a working IHD for 12 months after the smart meter is installed. There is no obligation on the type of IHD. There is no obligation after 12 months.
From an environmental point of view it does make sense for suppliers to use up an any stock of IHD3 that is manufactured so it doesn't end up in landfill immediately.