Wasn't sure this was worth a post as most people who might be into it would probably already have it but for those that don't this is it in its cheapest form.
You will need to be part of mynintendo which is the evolved form of the vanquished club nintendo. One of the rewards currently on offer is for a 15% discount on the digital version of Person Q from the eshop. The 15% code costs just 250 platinum points which is pretty easy to sort out.
The grand total for your hard work is a digital copy of Persona Q for £15.29 which is pretty cool imho. I had a physical copy and regret passing it on as it is a great mashup title and very polished from memory.