The front VW badge from the GTI will not fit on the GT Sport grille. The GT Sport VW emblem is 150mm across and has an extra lip to snugly fit on the GT grille, the GTI one will just slip through the hole!
Part number is 1K5 853 600 MQH and can be had for about a tenner. My uncle had the same dilemma for his Passat B6 where he upgraded his grille from midline to highline only for the badge to fall in! Got it from
this seller and all is well in the end!