Where can I find replacement glass for a coffee table (90 cm X 90cm)

many large Brico's have a supply of glass of various types which can be cut to order

More than probably, if you are needing replecement glass it was because the glass was not strengthened/toughened, You cannot buy this sort of glass from Brico.
Sorry did various 'verre renforcé' etc but didn't find anywhere

www.vitrerie50.be
VMC Vitrerie-Miroiterie du Cinquantenaire, 57 rue des Celts, 1040 Bruxelles,
open wednesdays 10h-12h Fridays 10-12 14-18
or telephone anytime TEL/FAX 02-733 26 04 GSM 0475 839 737
Guy Van Holsbeek, such a nice man & his son, will supply all types of glass for all kinds of use .
They also replace cracked windows, frame pictures, everything to do with glass super small family firm.