If you're really trying to get the zipper size to match you could look at orgXIII.org they have gaint zippers that you normally couldn't find at a fabric store. I bought the #30 and used it for my 2nd uniform.
As for the wig I would suggest getting the Magnum or Magnum long just to be safe. It's a wonderful wig for spiking and I love mine to death XD
God Tier Dave- 60% complete
Zora Suit Link (masquerade cosplay)- 40% complete
God Tier Vriska- complete
Azula- 0% complete
Phoenix Comic-con 2013:
Allen Walker 1st Uniform: 10% complete