Finding the right gloves can be tricky. The first pair of gloves I bought for my Pyro cosplay I got an an army surplus store. They were green and I spray painted them black and yellow. I do NOT recommend this. The paint just chips off.
My second pair of gloves I got around Halloween at a Value Village (thrift store). They are yellow "superhero" gloves (you can also find these online for pretty cheap). I used a thick black permanent marker to colour in the black areas. This worked alright. The black has stayed on and hasn't faded.