I've had several enquiries about adding tacks to character shoes - including a couple from people who were sold character shoes as flamenco shoes, and didn't discover their mistake until too late.
I have bad news, I'm afraid - you can't add nails to character shoes, or any other normal shoe for that matter.
The soles of most shoes are too thin to take tacks - the points will eventually poke right through and into your foot. If the shoemaker uses smaller tacks to avoid that problem, they're unlikely to stay in the shoe for long! The average sole isn't strong enough to take the stress of all that extra metal, either.
You might get away with adding nails to tap shoes or Irish dancing shoes, both of which have stronger soles to support the weight of metal plates. However, finding a cobbler who understands how to layer flamenco tacks is another challenge altogether!
If you want to make a flamenco sound with your feet, there really is no substitute for proper flamenco shoes.