Looking around the internet showed that a few kite companies sell kite stakes, but none of these looked especially nice. Until I stumbled across LS Kite Accessories. They make really nice-looking kite stakes, and the price, including shipping from the US, was very reasonable.
And here they are!
They look even better than on the pictures, and come complete with holsters and carabiners.
Blue ones for me, red ones for Irma; and dark ones for on a beach, lights ones for on grass. Really nice set of sturdy and well-made stakes. And the cherry on the cake was that the parcel escaped the attention of HM Revenue & Customs!