Here’s what I wound up with:
In the bottom right is a plastic case with my 18650 batteries. In the middle right is a USB charger, with a 6 foot USB cable on the bottom left. Top right is the printer.
It’s my first time cutting foam in a case like this, so the cuts are ugly, but it holds well. I’d say it’s good for light travel and storage.
Only $22 on Amazon: https://smile.amazon.com/gp/product/B013UCNTDE/
If you want heavier duty, my research led me to this Lykus case; I haven’t tested it but seems like it would fit, it’s more durable, and it has easier pluckable foam, for $43: https://smile.amazon.com/gp/product/B07YHL5SNG/