I am in Year 6: Spectrespecs (PS3 version) and have got the spectrespecs at Hogsmeade Station. When following Nick to the gate I need another pair of spectrespecs from the mailbox but I can only get a cartoon out of it and no spectrespecs. How do I get the spectrespecs so I can open the gate?
Since you mentioned following Nick, I infer you are playing the To the Next Mission - Young Dumbledore, Draught of Living Death level.
If you have unlocked the gold brick (as you stated you did) then you should have no issue retrieving the pair of spectrespecs to unlock the gate. Generally if you don't receive an item from a box it's because you have the item activated already, it's always worth double checking your spell wheel and see if you have the option available.