Although it has taken nearly five years to raise the first two thirds, Camelot said it was confident the remaining £250m would be raised in time, despite the bulk of building work for the new sports facilties needing to take place during the next 12 months.
The Dream Number lottery draw and certain scratchcards all feed into the pot that will help pay for the Olympic Stadium, VeloPark, Aquatics Centre, Handball Arena and Hockey Centre.
Camelot CEO Diane Thompson said that National Lottery retailers were playing a fundamental role in making sure that London 2012 was "the greatest sporting event that nation had ever seen" through selling specially designated games.
Camelot launched five scratchcards for London 2012 last year and is introducing two new games in June, Double Red Hot 7's, with a £77,777 top prize, and Mystic Dog with a £6,000 prize.
The £750m fund is part of the wider lottery contribution of £2.2bn total coming from National Lottery good causes money.