I found a solution by buying one of those cards that are blank inside, enabling me to craft my own bespoke message.
And to save killing further trees I also put "Happy Easter and Merry Christmas" in the card too. It's never too early, is it?
Mrs B also has the birthday / Mothers Day combo tomorrow.
And do you know what?
I've not been able to find a single card that covers both off, so I'm going to have to buy TWO cards.