As mentioned in the previous log, I don't have a bespoke solution for batteries yet. This is the area that needs the most improvement at this time.
Currently, the working plan is to stack up 3 LR44 batteries in-line with the PCB, as shown. This has the advantage of being small, axially balanced, and in the right voltage range. That last point is not critical, as I could work with 3V, or throw a boost converter on there if the blue LEDs require.
My initial thought was to throw a wide zap-strap on there to hold the batteries in, and form some copper contacts on either end to make electrical contact.
This is janky and I'd like a better solution! Let me know if there are any. An off-the-shelf axially-mounted battery holder would be boss, but I don't think they exist.