Re: Alfa Spider quarterlight window catches
How do chap, welcome along.
Are the catches glued directly to the glass? If so then the best thing to use is Loctite construction adhesive (plus activator) but it's pretty expensive for one little blob you will require.
Pop into your local Autoglass, as this is what they use for re-attaching rear view mirrors to windscreens.
There is a branch in Taunton (Unit 3 Priory Way Industrial Estate, Priory Way, TA1 2AL Taunton)
thye will no doubt sort you out for the price of a pint.