Everything you need to know about.
Fumos are a line of high-quality plush character figures manufactured and sold by the Japanese company Gift. Fumos exist for multiple franchises, but most notably the Touhou Project. Touhou Fumos are designed by Royalcat.
Fumos are generally difficult to purchase, even in Japan, due to their relative scarcity. Fumos are out-of-stock as a rule, and Gift typically only manufactures them twice a year, when they open for limited pre-orders. For most restocks, Gift does not ship outside of Japan; when they do, the sales go through the AmiAmi store.
The word "Fumo" comes from the Japanese onomatopoeia "モフモフ" (mofumofu), which means "soft to the touch", or "fluffy".
Check out the colection Here. You can also look through the entire Gift catalog here.
That was most likely a custom fumo! There are quite a few people out there who make custom fumos themselves.
You have two main options: find a trustworthy reseller at a reasonable price, or order one from Gift directly using a Proxy or Forwarding Service. You may need to use both, depending on the reseller.
The same things you need for any other online shopping:
Bootleg fumos, mimicking the Fumo style and passed off as being authentic, are often cheaper than real ones. However, Some have their own character and value, like the long-legged bootleg dekas, but many do not. You'll have to decide on your own, but know that you're taking a risk. For information on avoiding bootlegs, see the reseller guide.
There are plenty of online communities for discussing and sharing our soft friends. /jp/ on 4chan regularly has fumo related threads. r/fumofumo on reddit also is a nice place to post fumos, and there are several fumo-related Discord communities like Fumo Project.
Fumo.