I highly doubt an anime sewing class exist since cosplaying isn't very common with everyone. You are better off taking a regular sewing classes from an art school or teaching yourself how to sew. Jut like what PSY-chan said, theater classes may have classes.
Noiz [DRAMAtical Murder] 70%
Okita Souji [Hakuouki] 90%
Riku [Kingdom Hearts II] 70%
Yusei Fudo [Yu-Gi-Oh! 5Ds]
Chrome Dokuro [Katekyo Hitman REBORN!]
Armin Arlet or Levi [Shingeki no Kyojin]