I bought my Kobo Clara HD direct from
https://uk.kobobooks.com this time last year. Very easy, and it was the lowest price at the time. I think shipping is from EU but it's still very fast and free too. I just checked the price vs amazon UK and the amazon price is much higher. John Lewis charge the same as Kobo but have no stock. Argos are the cheapest by a long way. I bought a really good case on aliexpress:
https://www.aliexpress.com/item/32894396288.html It's just the right thickness to offer some protection (unlike a lot of the very flimsy cases out there), is magnetic just like the official case, and fits perfectly.