So it has been announced on the official Digimon 20th twitter account that Digimon products will be available to buy from GraffArt event.

There will be a range of different products on sale for the Digimon Adventure 20th anniversary.
The event will start of the 20th of March which is just a month away but there is currently not end date. They do have a website but Digimon is currently listed just yet.
There are a range of different items such as clearfile of the key art, badges, phone cases and much more!
The products are exclusively for this event so if you are wanting something you are best to contact a proxy service like FromJapan or wait until the products appear on places Yahoo Auctions JP.