Where's the Magcargonite?

Does anybody know where to find Magcargonite? Mega Magcargo is easily my favorite out of fake mega evolutions. So, it would be greatly appreciated if someone could reply.

there is a girl in a house in amphrite city who lost her hypno go back to the route she says and find the hypno come back to her house which is close to the northern end! 350px-AmphitriteCity|350x396

yeah the most northern house I tried to show a picture but it is on the left