@Vapaneezer Scrooge thinking about the same. There are 2 options that I found sound. First is to make the battery compartment about 4 mm taller than the battery, then glue battery contacts to it. Flat ones like it the pic are much nicer than spring like ones.
Second option is to use springy battery department. Sound odd but found a few on thingiverse. Check the second pic. Just needs a contact but it's springy on its own and should last a long time if printed with filament that is a little bit flexible like PETG. Just search thingiverse for flexing battery holder. Hope it helps...
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