I also make my own flapjacks - maybe if you cut and wrap them right after making them, and store them with your bike kit, they’ll survive the hungry mouths in the house? They don’t really go off that quick.
I also buy oat bars (cheapo ones), there is so much choice now, some aren’t too bad from the ingredients. Lidl has own brand bars that are like Nakd bars (mainly dates, natural ingredients), but cheaper.
If you make your own rice cakes, you can also make savoury ones. Basically just cook sticky rice, mix with whatever you want it to taste of while hot, then compact it into a small tin (about an inch thick), chill and cut and wrap. I like mine with apple and cinnamon, but you could mix it with pizza sauce for a pizza one, or whatever you fancy. They keep in the fridge for a few days, though I always sniff them and bin when I’m not sure.
Alternatively, toast with jam is easy and quick to take.