Here is my new DIY crate in my bike.
I did order a pannier like messenger bag for my laptop but I am still waiting!
Most trips for me are handled with a front basket, if I am running around.
Today I'm headed to a cook off at a local brewery. Just enough space for my purse and any random stuff I might accumulate during an average day.
It keeps me worry free if I realize later I need to grab some milk or something. So I don't need to feel ultra prepared for any possible errand by bringing another bag and so on. My purse is heavy enough without having to hold extra bags and such. (I do have space for my lights in my purse, and a high-vis vest if I am headed on a darker or less busy bike route).