I present my second Tritium Pendant, for use with a 3x12mm tritium vial (tritium vial not included).
The attachment hole is 2.3mm by 2.6mm, so it should be large enough for a fine necklace chain (if the chain's end ring can be opened), or small attachment ring.
The tritium vial 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.
Before gluing, please ensure that the vial fits loosely into the lantern body and that there are no tight spots. Due to potential irregularities in the printing process, some gentle drilling may be required on the tritium vial channel, to ensure an unobstructed fit of the vial, into the lantern.
I have a few assembled tritium items available from my Etsy shop
(tritium vials glued in place with Norland 61 and split ring installed).
There are some more photos of this object and other examples of my work, both 3D printed and otherwise, on my 'Tofty' facebook page