Scoured the food presses to find a replacement, but only managed to find a mixed seed selection (pumpkin, sunflower and sesame seeds). What's the worst that can happen? (combustion is unlikely).
So after the Microwave alerted me to the porridge's cooked state, I added a good handful of the mixed seeds, and the usual quantities of honey (a good squeeze) and cinnamon (a healthy scatter), I gave the mixture a quick stir and allowed it to rest for a minute or two.

Delish! A lovely crunchiness is introduced, and the seeds must have released some oils to give the porridge a slightly nutty taste. I'm not sure that the banana will be permanently relegated to the fruit bowl, but it might find that it has to fight for space in the porridge bowl in future, alongside the sunflower seeds, pumpkin seeds and sesame seeds.

I'm a long distance runner, and there really is no better way to prepare for a long run (particularly in cold wet Ireland) than a big slurpy bowl of porridge (now with extra seeds!).