I first saw it in Europe a few years ago, and now it's everywhere this Winter in the 'States. The slim bubble coat & bubble vests range from moderate to expensive. The silhouette is slim and form fitting for a modern fit, as opposed to the down coat trends of the 90's, you remember the oh so 90's First Down brand coat.
I have mostly seen the bubble vest paired under a herringbone or tweed blazer which is the most stylish way to show it off. The bubble vest is a more compact of a vest compared to the larger down variety, so it is not bulging out, making the blazer fit tightly.
I can give tips to find it cheaper and I can list the more expensive types. You can always compare prices with the site shopstyle. As you can see the vest ranges from $50-$500. The cheapest I have seen this gold mine of a find is at Costco...yes Costco! I cannot remember the name of the brand that it is made of but it costs about $15. If you don't have a Costco membership, which is a terrible thing because the vest ther are the most inexpensive and the quality is just as good as other brands. Uniqlo is one of the brands ranging in the 50's. H and M also has a down coat and down vest for $50. If you are looking to stand out Denim and Supply offers a camo vest that does not constitute as a bubble vest, it is more in the category of a larger down vest.