Ktown4U, originally DVD Heaven, is an online retailer that sells official Kpop merchandise. They have a new product strategy where some of their new items will include a folded poster; in the product title, it'll be something like "Poster + (Product)". On the product page, it asks if you want a poster tube for about $1.85 extra (plus extra shipping for the tube).
For Infinite's Official Collection Card Vol.2, there are two random posters. I ordered two sets, therefore I'd get two posters. To guarantee getting two different posters, I wrote in the Shipping Memo "please send two different poster designs."
Ordering from this site is a little confusing. After putting your items in the cart, you enter your shipping information. They ask if you want to label your package as "merchandise" or "gift" and to determine the monetary value of the package, with the default value being the price you're paying. I think all of this is for import fees, but I just chose "merchandise" and the default value, and I didn't have to pay any extra fees through my mail service. After finishing this step, you submit it. Then you have to go to a separate page to pay, which I did via PayPal. I guess they don't have the payment in the same section as the shipping area so Ktown4U can hold onto your order for a few days until you pay.
For two sets, my total was about $63.50, and shipping, which is determined by weight and the shipping method chosen, was about $12. I chose registered small packet for my shipping, because I think these companies won't help you if you get unregistered shipping and your package gets lost. My packaged was shipped a day before the official release date (it was weird, officially it should be June 26th, but everyone seemed to get it on the 25th) and arrived in 13 days. Because it's registered, you have to sign for the package.
Overall, I think my go-to online shop would be Ktown4U, because I love getting a free folded poster for cheaper than buying without a poster from other places. I also pre-ordered the limited version of Infinite's "Reality" mini album, so we'll see how well they ship more fragile items.