The Mimikyu card will be available in just over 12 hours from the time of this post. You’ll be able to buy it from the Japanese Pokémon Center website here: www.pokemoncenter-online.com/?p_cd=4521329246291. It has a markup of 486 JPY (including tax), which is roughly $4.34. They’re limited to 1 per person.
Some of the other cards have already made their way onto eBay for absolutely absurd prices*. Not only are these cards not available yet, this particular Pikachu sold for over 45 times the RRP. If you really want to get your hands on these cards, simply use a proxy service to buy direct from the online Japanese Pokémon Center shop, or wait until they inevitably find their way onto the various Japanese marketplace websites and search for “ポケモン ムンク展”.
As far as I’m aware the cards are being released periodically between now and January. I’m pretty sure most of the current eBay sales are currently in breach of eBay’s presale listings policy, which states that items must be shipped to the buyer within 30 days. Be careful with your money and don’t get scammed.
* Seems that listing no longer exists. That was quick! It was a Pikachu card which had received over 50 bids and sold for something like $195.