New here need a few tips.

My friend went as a vampire one year and she actually got the Elvira dress and it worked out perfectly - she just didn't wear the belt or the wig. It's really easy to get ahold of a "plus size" Elivra costume - and sometimes these cheap-o synthetic Halloween dresses are stretchy and roomie!

You don't necessarily have to get a specific "Vampire" costume - any dark black dress will do. For a pirate one year I bought the Scream costume, but I cut it up real short and made some extra slices on it, threw on a big chunky belt and it worked fine! The dress, I noticed, was really, really roomie (and I am not a teenie tiny lady!) and could be considered "plus size."

Corsets are great, as well - They come in a number of sizes. And if you want some cool arm warmers (if you want to go a little gothic), cut the crotch out of some tights or fishnets and put your arms through the legs - those work fantastic and they fit anyone! That could be a cool accessory. Piecing together a costume is sometimes a better idea!

Google works great, as mentioned already :: vampire costume plus - Google Images

Honestly, anything black or purple works perfectly, too