Help! Hogwarts Crest?

[Jamieson Wolf Villeneuve]

Hello Everyone! 

I need your help. I'm planning on dressing up as Harry for Halloween...I already have the Gryffindor scarf, Harry's Wand and I already wear glasses. I'm even having a friend make school robes for me. 

But I need your help! Does anyone know where I can purchase/buy a Hogwarts crest badge that I can sew onto the robes? I've checked Amazon and the Leaky Cauldron shop, but came up with nothing. 

Any help would be grand! 

Cheers,
Jamieson (who is very much looking forward to seeing HP and the HBP Movie!)