You can find Flimm, the "sales freak", in Flipside, on the other side of the water on B1, or in the Pit of 100 Trials in Flipside or Flopside. You can find Flamm the "map chap" on the other side of the water in B1 of Flopside.
FlimmEditIf you go to Flimm on B1 of Flipside You will find him selling things such as rare Cards and rare drops from enemies (Such as Big Eggs or Fresh Veggies). You can also occasionally find him standing next to the door on "Checkpoint floors" of the Pit of 100 trials, where he will be selling mostly Items that would be useful in the Pit of 100 trials (Such as Shroom Shakes and Thunder Rages).
In normal gameplay, Flimms prices for items are extremely high, but in the Flipside Pit of 100 Trials, they are significantly lower.