The loop earplug case by Waffle was aaaaaalmost perfect, but I found myself sometimes dropping the outer case when I was in a hurry and trying to get my loops out when walking. 

All I've done is added a small retention lip to both the inner and outer parts of the case. You'll need to give it a little push to slot together, but PLA has enough give to not be an issue. 

Once together, the retention lip will stop the outer case sliding all the way off. Simple but helps alot!

FOR LOOP SWITCH 2: Some helpful community members tested and found that 103% - 105% will fit the Switch 2 (it's a bit bulkier than standard Loops)

PLEASE NOTE: There is a recess on the bottom of the inner part that gets hidden by the support material. Don't forget to pull this out before slotting together!