Cinderella's wicked stepmother is a Disney costume that is quite rare; in fact, I've only seen parts of it. Not quite a whole costume, but here are some ideas on putting one together.
So what could you do, to put together such a costume, if you wanted to play Cinderella's wicked stepmother?
For one, the story says she is very vain. That being the case, I would expect plenty of makeup and a fine dress. Not to mention plenty of jewelry to go with it!
As for the hair...hmmm. I'd either choose an upswept brunette or gray wig. Maybe put some more jewelry on the wig (like a fancy comb). I go back and forth on the hair color. If she's vain, she might try to dye it. On the other hand, dyes weren't all that common back then. So, your choice on how to handle it!
The problem with this costume is that most people won't recognize it. Unless, of course, you are going to a Cinderella party!
OK, so you don't want to go as Cinderella or the Fairy Godmother. If you're still interested in playing, umm, a "bad character", can I suggest Maleificent from Sleeping Beauty instead? This costume is fairly easy to find in adult sizes (below).
WOMENS DISNEY MALEFICENT DISGUISE DELUXE ADULT BLACK HORNS PARTY VINYL COSTUME
Time Remaining: 16d 1h 21m
Buy It Now for only: $20.74
Maleficent Costume Deluxe Adult Disney Halloween Fancy Dress
Time Remaining: 21d 9h 17m
Buy It Now for only: $57.69
Womens Disney Maleficent Disguise Deluxe Adult Black Horns Halloween Costume
Time Remaining: 15d 16h 7m
Buy It Now for only: $42.99
BRAND NEW Licensed Disney Movie DELUXE ADULT MALEFICENT COSTUME Sizes S M L
Time Remaining: 26d 13h 6m
Buy It Now for only: $22.95
Maleficent Horns Disney Deluxe Adult Costume Headpiece Womens Fancy Dress
Time Remaining: 8d 9h 19m
Buy It Now for only: $38.00
Maleficent Costume Deluxe Christening Gown Adult Womens Halloween Fancy Dress
Time Remaining: 14d 2h 2m
Buy It Now for only: $37.99
Maleficent Movie Sexy Evil Sorceress Witch Adult Womens Halloween Costume New L
Time Remaining: 22d 13h 39m
Buy It Now for only: $49.95
Maleficent Christening Black Glam Deluxe Adult Costume
Time Remaining: 18h 28m
Buy It Now for only: $39.99
Maleficent Deluxe Adult Women Costume Movie Villain Wicked Theme Party Halloween
Time Remaining: 10d 23h 29m
Buy It Now for only: $39.95
While I haven't been able to show you a Cinderella's Wicked Stepmother costume, I hope I've given you some ideas. Enjoy the hunt!