Glue that withstands boiling water?

I’ve got a 3 litre “air pot” vacuum flask that I fill each day with solar-heated water. The plastic spigot into which the stainless steel dip-tube pushes has split, so the tube falls out. It’s not possible to tighten it up mechanically. I’ve tried epoxy - that turns red and disintegrates. I’ve tried Everbuild Stixall which claims to withstand 100°C and has lasted some time but is now going the same way. I’ve not tried Superglue because I read that that won’t work. Any other suggestions? Thanks.

Epoxy?

Two-part epoxy resin. I used rapid - perhaps “normal” would have been better.