If you can point out exactly where the pumpkin set can be purchased I will edit that out from the suggestion but I have not seen anything like that in any of the clothing shops I have visited - as far as I can tell (from gameplay and the wiki), unless it can be found in the arc area that requires a pass (acquired via a quest line) to enter, the island area or locked behind the 'invincible' plant then I'm fairly certain its not in the game currently.
The general idea of the suggestion was some more costume themed clothing items if you want to dress you the character in something a little bit more whimsical then the generally practical or lewd options available in most stores.