What's the stuff used to fix upvc trim to windows?

Hello

A piece of narrow trim has come off of our windows.
It's a long piece of 'quadrant' type trim that goes between two panels of a bay window.

I remember the guys using some glue type stuff that dries white and hard.
I've got a spare bit of trim but am wondering where to get this glue stuff.
I don't want to use caulk or frame sealant if I can avoid it.

Thanks

You are dead right not to use Caulk or frame Sealant, they are not made for the job.
I always use a product called Fixall, it sticks really quickly and your quadrant definately won't fall off again