Please tell me where to buy A380 aircraft model?

Majority of aircraft model shops will have A380 for sell... You can try West Main Model and their address is:
Shop 251, 2/F,
Pioneer Centre,
750 Nathan Road,
Mongkok, Kowloon

There they would have a pretty big selection of A380 model from 1:200 to 1:1000 in scale... And from Airbus old livery A3XX to the new livery A380 and Herpa Wing 1:500 A380 in airlines livery like Lufthansa/Air France/Qatar/Etihad Airways etc...
Just go and have a look and ask tell them that you would like A380 and the scale you like... The shopkeeper will show you a large collection of them... And you may get a small discount if ask her to lower the price... Usually you get bigger discount as you buy more...