Most of the shops used to buy MeseMoa. merchandise do not ship internationally, and some of them do not even accept online payment. The most common methods for buying from these shops are using a proxy purchasing system or a proxy forwarding system. If possible, you could also rely on a friend living in Japan who's willing to buy items on your behalf.
Here you can find a work in progress Google Drive containing guides to using some of the common sites to buy MeseMoa. and DD Company merchandise. You can also find other guides online, such as this site which summarises the main selling points of various proxy sites.
This is where you pay a person or company to buy the item on your behalf and send it to your address overseas. Some companies will also assist you to bid on second-hand items through online auctions. Usually you are required to submit your request for an item and pay before they will buy it for you. Once your item reaches the company warehouse in Japan, you then have to pay any shipping fees, as well as a service fee. Examples of proxy purchasing systems are From Japan and Zen Market. Each company has their own fees, so search around to see what suits you best.
Use if:
The first payment must be made by cash on delivery (as with the MeseMoa. Shop)
The website does not accept online payment from overseas
You're not confident in using Japanese to make the purchase yourself
This is where you register with a company who will give you an address at their warehouse in Japan. Whenever you buy something online, you can have it sent to this address, from where they will forward it to your address overseas. Once the item reaches the warehouse address, you'll have to pay shipping fees and a service fee. To register an address, you may need to provide proof of ID. Examples are Tenso and Blackship. Make sure to check the terms of use carefully, as most sites will not accept items which require payment on delivery.
Use if:
You are able to make the payment online from overseas
You need a Japanese address to register with certain sites (e.g. the official fanclub)
You feel confident that you can make the purchase in Japanese (some shops also have English versions)
What is the exchange rate between your currency and Japanese yen?
Does your bank account charge you for making payments in foreign currency?
Does your country require you to pay customs tax on incoming parcels from Japan?
If buying a DVD, is your DVD player able to play DVDs from Region 2?