I present my small "Birdcage" decorative bead, designed to hold twelve of the 2x8mm tritium vials (tritium vials not included), but will work just as well without.
This model is sized for printing in stainless steel or one of it's variants, for the model sized for printing in plastic,silver or brass please check my shop.
The central hole is 5mm in diameter and should just be wide enough for two lengths of 550 paracord.
The tritium vials should be set using a UV activated optically clear adhesive such as Norland 61 or Loctite glass bond. These adhesives will cure in direct sunlight in an hour or so.
There are some more photos of this object and other examples of my work, both 3D printed and otherwise, on my 'Tofty' facebook page.