The Flux Store was created on November 21st, 2014 as part of the Flux Remix. It is, unsurprisingly, a store in The Flux. There, you can trade complete sets of Flux items for 8 flux dust (). You can also buy the following items:
(Note: There is a 2nd Store in the Flux named the Very Expensive Item Store which has its own page.)
The Super Trinket has its own page.