Epoxy (e.g. Araldite) or aquarium-sealant.
Or that acrylic cement that welds the plastics together by means of a solvent that temporarily liquefies the plastic.
Yes that thing I can't remember the name of... I don't know what's needing to be built here - beyond your clairvoyance, or reserving judgment?
I literally forget its name - other than 'plastic solvent welder' or something.